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	$122.42	6.219%	$130.0333	$130.03	$130.05	$130.00
Purchase #2	$147.64	9.836%	$162.1619	$162.16	$162.15	$162.20
Purchase #3	$74.93	11.111%	$83.2555	$83.26	$83.25	$83.30
Purchase #4	$164.82	9.644%	$180.7152	$180.72	$180.70	$180.70
Purchase #5	$192.52	9.486%	$210.7824	$210.78	$210.80	$210.80
Purchase #6	$111.47	6.297%	$118.4893	$118.49	$118.50	$118.50
Purchase #7	$250.69	7.737%	$270.0859	$270.09	$270.10	$270.10
7 purchase totals =	$1,064.49		$1,155.5235	$1,155.53	$1,155.55	$1,155.60