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	$114.66	12.115%	$128.5511	$128.55	$128.55	$128.60
Purchase #2	$237.33	4.643%	$248.3492	$248.35	$248.35	$248.30
Purchase #3	$67.97	5.328%	$71.5914	$71.59	$71.60	$71.60
Purchase #4	$36.42	3.453%	$37.6776	$37.68	$37.70	$37.70
Purchase #5	$113.49	9.828%	$124.6438	$124.64	$124.65	$124.60
Purchase #6	$242.55	5.359%	$255.5483	$255.55	$255.55	$255.50
Purchase #7	$190.79	7.393%	$204.8951	$204.90	$204.90	$204.90
7 purchase totals =	$1,003.21		$1,071.2565	$1,071.26	$1,071.30	$1,071.20