Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$232.38	12.618%	$261.7017	$261.70	$261.70	$261.70
Purchase #2	$113.81	12.349%	$127.8644	$127.86	$127.85	$127.90
Purchase #3	$125.67	6.711%	$134.1037	$134.10	$134.10	$134.10
Purchase #4	$103.38	7.825%	$111.4695	$111.47	$111.45	$111.50
Purchase #5	$151.75	8.351%	$164.4226	$164.42	$164.40	$164.40
Purchase #6	$149.45	4.477%	$156.1409	$156.14	$156.15	$156.10
Purchase #7	$232.76	4.165%	$242.4545	$242.45	$242.45	$242.50
7 purchase totals =	$1,109.20		$1,198.1573	$1,198.14	$1,198.10	$1,198.20