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	$212.55	4.856%	$222.8714	$222.87	$222.85	$222.90
Purchase #2	$122.57	4.317%	$127.8613	$127.86	$127.85	$127.90
Purchase #3	$204.29	10.754%	$226.2593	$226.26	$226.25	$226.30
Purchase #4	$77.71	10.843%	$86.1361	$86.14	$86.15	$86.10
Purchase #5	$128.43	4.728%	$134.5022	$134.50	$134.50	$134.50
Purchase #6	$208.54	4.585%	$218.1016	$218.10	$218.10	$218.10
Purchase #7	$229.92	3.624%	$238.2523	$238.25	$238.25	$238.30
7 purchase totals =	$1,184.01		$1,253.9842	$1,253.98	$1,253.95	$1,254.10