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	$71.81	9.398%	$78.5587	$78.56	$78.55	$78.60
Purchase #2	$146.94	12.626%	$165.4926	$165.49	$165.50	$165.50
Purchase #3	$194.88	10.785%	$215.8978	$215.90	$215.90	$215.90
Purchase #4	$221.66	13.614%	$251.8368	$251.84	$251.85	$251.80
Purchase #5	$86.86	4.415%	$90.6949	$90.69	$90.70	$90.70
Purchase #6	$119.36	4.698%	$124.9675	$124.97	$124.95	$125.00
Purchase #7	$229.58	8.337%	$248.7201	$248.72	$248.70	$248.70
7 purchase totals =	$1,071.09		$1,176.1684	$1,176.17	$1,176.15	$1,176.20