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	$223.90	8.576%	$243.1017	$243.10	$243.10	$243.10
Purchase #2	$11.90	7.385%	$12.7788	$12.78	$12.80	$12.80
Purchase #3	$128.32	6.383%	$136.5107	$136.51	$136.50	$136.50
Purchase #4	$219.47	6.230%	$233.143	$233.14	$233.15	$233.10
Purchase #5	$69.76	10.345%	$76.9767	$76.98	$77.00	$77.00
Purchase #6	$98.30	10.436%	$108.5586	$108.56	$108.55	$108.60
Purchase #7	$189.29	8.425%	$205.2377	$205.24	$205.25	$205.20
7 purchase totals =	$940.94		$1,016.3072	$1,016.31	$1,016.35	$1,016.30