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	$209.63	6.603%	$223.4719	$223.47	$223.45	$223.50
Purchase #2	$95.91	12.805%	$108.1913	$108.19	$108.20	$108.20
Purchase #3	$190.57	3.131%	$196.5367	$196.54	$196.55	$196.50
Purchase #4	$230.26	9.116%	$251.2505	$251.25	$251.25	$251.30
Purchase #5	$205.45	13.801%	$233.8042	$233.80	$233.80	$233.80
Purchase #6	$101.54	7.371%	$109.0245	$109.02	$109.00	$109.00
Purchase #7	$41.87	9.681%	$45.9234	$45.92	$45.90	$45.90
7 purchase totals =	$1,075.23		$1,168.2025	$1,168.19	$1,168.15	$1,168.20