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	$235.30	12.718%	$265.2255	$265.23	$265.25	$265.20
Purchase #2	$57.34	3.456%	$59.3217	$59.32	$59.30	$59.30
Purchase #3	$84.79	6.725%	$90.4921	$90.49	$90.50	$90.50
Purchase #4	$164.28	8.779%	$178.7021	$178.70	$178.70	$178.70
Purchase #5	$211.76	7.566%	$227.7818	$227.78	$227.80	$227.80
Purchase #6	$154.41	12.568%	$173.8162	$173.82	$173.80	$173.80
Purchase #7	$75.43	10.279%	$83.1834	$83.18	$83.20	$83.20
7 purchase totals =	$983.31		$1,078.5228	$1,078.52	$1,078.55	$1,078.50