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	$106.70	6.245%	$113.3634	$113.36	$113.35	$113.40
Purchase #2	$228.25	4.330%	$238.1332	$238.13	$238.15	$238.10
Purchase #3	$115.73	4.116%	$120.4934	$120.49	$120.50	$120.50
Purchase #4	$74.87	11.355%	$83.3715	$83.37	$83.35	$83.40
Purchase #5	$179.51	12.245%	$201.491	$201.49	$201.50	$201.50
Purchase #6	$109.70	3.104%	$113.1051	$113.11	$113.10	$113.10
Purchase #7	$133.56	11.267%	$148.6082	$148.61	$148.60	$148.60
7 purchase totals =	$948.32		$1,018.5658	$1,018.56	$1,018.55	$1,018.60