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	$42.51	11.626%	$47.4522	$47.45	$47.45	$47.50
Purchase #2	$171.82	13.147%	$194.4092	$194.41	$194.40	$194.40
Purchase #3	$119.34	4.148%	$124.2902	$124.29	$124.30	$124.30
Purchase #4	$166.47	5.739%	$176.0237	$176.02	$176.00	$176.00
Purchase #5	$138.64	3.467%	$143.4466	$143.45	$143.45	$143.40
Purchase #6	$195.83	5.625%	$206.8454	$206.85	$206.85	$206.80
Purchase #7	$153.95	13.113%	$174.1375	$174.14	$174.15	$174.10
7 purchase totals =	$988.56		$1,066.6048	$1,066.61	$1,066.60	$1,066.50