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	$99.89	13.250%	$113.1254	$113.13	$113.15	$113.10
Purchase #2	$50.75	3.114%	$52.3304	$52.33	$52.35	$52.30
Purchase #3	$104.32	4.386%	$108.8955	$108.90	$108.90	$108.90
Purchase #4	$110.90	6.488%	$118.0952	$118.10	$118.10	$118.10
Purchase #5	$184.56	3.540%	$191.0934	$191.09	$191.10	$191.10
Purchase #6	$66.49	13.643%	$75.5612	$75.56	$75.55	$75.60
Purchase #7	$156.75	10.439%	$173.1131	$173.11	$173.10	$173.10
7 purchase totals =	$773.66		$832.2142	$832.22	$832.25	$832.20