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	$67.73	13.434%	$76.8288	$76.83	$76.85	$76.80
Purchase #2	$39.87	6.610%	$42.5054	$42.51	$42.50	$42.50
Purchase #3	$70.58	9.834%	$77.5208	$77.52	$77.50	$77.50
Purchase #4	$101.79	7.772%	$109.7011	$109.70	$109.70	$109.70
Purchase #5	$238.49	12.833%	$269.0954	$269.10	$269.10	$269.10
Purchase #6	$229.76	10.360%	$253.5631	$253.56	$253.55	$253.60
Purchase #7	$238.93	11.870%	$267.291	$267.29	$267.30	$267.30
7 purchase totals =	$987.15		$1,096.5056	$1,096.51	$1,096.50	$1,096.50