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	$216.29	6.854%	$231.1145	$231.11	$231.10	$231.10
Purchase #2	$93.35	3.559%	$96.6723	$96.67	$96.65	$96.70
Purchase #3	$171.86	9.842%	$188.7745	$188.77	$188.75	$188.80
Purchase #4	$123.99	10.436%	$136.9296	$136.93	$136.95	$136.90
Purchase #5	$83.86	6.742%	$89.5138	$89.51	$89.50	$89.50
Purchase #6	$137.69	10.364%	$151.9602	$151.96	$151.95	$152.00
Purchase #7	$207.94	7.334%	$223.1903	$223.19	$223.20	$223.20
7 purchase totals =	$1,034.98		$1,118.1552	$1,118.14	$1,118.10	$1,118.20