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	$177.37	7.494%	$190.6621	$190.66	$190.65	$190.70
Purchase #2	$220.44	5.731%	$233.0734	$233.07	$233.05	$233.10
Purchase #3	$19.25	6.415%	$20.4849	$20.48	$20.50	$20.50
Purchase #4	$76.84	8.141%	$83.0955	$83.10	$83.10	$83.10
Purchase #5	$85.63	11.764%	$95.7035	$95.70	$95.70	$95.70
Purchase #6	$155.56	6.808%	$166.1505	$166.15	$166.15	$166.20
Purchase #7	$218.50	5.166%	$229.7877	$229.79	$229.80	$229.80
7 purchase totals =	$953.59		$1,018.9576	$1,018.95	$1,018.95	$1,019.10