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	$182.49	7.517%	$196.2078	$196.21	$196.20	$196.20
Purchase #2	$83.59	6.605%	$89.1111	$89.11	$89.10	$89.10
Purchase #3	$80.58	11.123%	$89.5429	$89.54	$89.55	$89.50
Purchase #4	$173.93	9.316%	$190.1333	$190.13	$190.15	$190.10
Purchase #5	$132.73	8.180%	$143.5873	$143.59	$143.60	$143.60
Purchase #6	$237.59	3.473%	$245.8415	$245.84	$245.85	$245.80
Purchase #7	$186.48	5.290%	$196.3448	$196.34	$196.35	$196.30
7 purchase totals =	$1,077.39		$1,150.7687	$1,150.76	$1,150.80	$1,150.60