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	$196.39	12.814%	$221.5554	$221.56	$221.55	$221.60
Purchase #2	$82.38	4.531%	$86.1126	$86.11	$86.10	$86.10
Purchase #3	$87.69	3.651%	$90.8916	$90.89	$90.90	$90.90
Purchase #4	$67.62	5.459%	$71.3114	$71.31	$71.30	$71.30
Purchase #5	$113.98	11.717%	$127.335	$127.34	$127.35	$127.30
Purchase #6	$72.67	9.112%	$79.2917	$79.29	$79.30	$79.30
Purchase #7	$140.47	9.630%	$153.9973	$154.00	$154.00	$154.00
7 purchase totals =	$761.20		$830.4950	$830.50	$830.50	$830.50