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	$92.28	13.678%	$104.9021	$104.90	$104.90	$104.90
Purchase #2	$218.74	6.624%	$233.2293	$233.23	$233.25	$233.20
Purchase #3	$150.60	11.336%	$167.672	$167.67	$167.65	$167.70
Purchase #4	$197.54	5.840%	$209.0763	$209.08	$209.10	$209.10
Purchase #5	$45.80	10.104%	$50.4276	$50.43	$50.45	$50.40
Purchase #6	$238.52	6.112%	$253.0983	$253.10	$253.10	$253.10
Purchase #7	$62.98	11.239%	$70.0583	$70.06	$70.05	$70.10
7 purchase totals =	$1,006.46		$1,088.4639	$1,088.47	$1,088.50	$1,088.50