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	$82.72	6.426%	$88.0356	$88.04	$88.05	$88.00
Purchase #2	$95.76	9.619%	$104.9712	$104.97	$104.95	$105.00
Purchase #3	$174.75	12.216%	$196.0975	$196.10	$196.10	$196.10
Purchase #4	$100.71	10.350%	$111.1335	$111.13	$111.15	$111.10
Purchase #5	$96.98	8.233%	$104.9644	$104.96	$104.95	$105.00
Purchase #6	$225.25	7.386%	$241.887	$241.89	$241.90	$241.90
Purchase #7	$25.44	10.128%	$28.0166	$28.02	$28.00	$28.00
7 purchase totals =	$801.61		$875.1058	$875.11	$875.10	$875.10