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	$215.79	8.799%	$234.7774	$234.78	$234.80	$234.80
Purchase #2	$179.25	6.789%	$191.4193	$191.42	$191.40	$191.40
Purchase #3	$192.72	12.240%	$216.3089	$216.31	$216.30	$216.30
Purchase #4	$59.89	8.807%	$65.1645	$65.16	$65.15	$65.20
Purchase #5	$151.25	9.873%	$166.1829	$166.18	$166.20	$166.20
Purchase #6	$176.40	3.253%	$182.1383	$182.14	$182.15	$182.10
Purchase #7	$247.30	8.325%	$267.8877	$267.89	$267.90	$267.90
7 purchase totals =	$1,222.60		$1,323.8790	$1,323.88	$1,323.90	$1,323.90