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	$90.87	11.121%	$100.9757	$100.98	$101.00	$101.00
Purchase #2	$12.38	11.657%	$13.8231	$13.82	$13.80	$13.80
Purchase #3	$84.67	13.837%	$96.3858	$96.39	$96.40	$96.40
Purchase #4	$124.52	5.144%	$130.9253	$130.93	$130.95	$130.90
Purchase #5	$181.53	13.804%	$206.5884	$206.59	$206.60	$206.60
Purchase #6	$42.75	6.459%	$45.5112	$45.51	$45.50	$45.50
Purchase #7	$58.30	6.626%	$62.163	$62.16	$62.15	$62.20
7 purchase totals =	$595.02		$656.3725	$656.38	$656.40	$656.40