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	$164.62	7.179%	$176.4381	$176.44	$176.45	$176.40
Purchase #2	$249.44	6.219%	$264.9527	$264.95	$264.95	$265.00
Purchase #3	$56.79	5.352%	$59.8294	$59.83	$59.85	$59.80
Purchase #4	$106.72	4.126%	$111.1233	$111.12	$111.10	$111.10
Purchase #5	$54.69	9.784%	$60.0409	$60.04	$60.05	$60.00
Purchase #6	$141.62	10.779%	$156.8852	$156.89	$156.90	$156.90
Purchase #7	$44.67	12.164%	$50.1037	$50.10	$50.10	$50.10
7 purchase totals =	$818.55		$879.3733	$879.37	$879.40	$879.30