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	$31.83	7.258%	$34.1402	$34.14	$34.15	$34.10
Purchase #2	$56.96	7.872%	$61.4439	$61.44	$61.45	$61.40
Purchase #3	$161.92	3.420%	$167.4577	$167.46	$167.45	$167.50
Purchase #4	$195.39	11.654%	$218.1608	$218.16	$218.15	$218.20
Purchase #5	$74.63	10.345%	$82.3505	$82.35	$82.35	$82.40
Purchase #6	$104.40	7.252%	$111.9711	$111.97	$111.95	$112.00
Purchase #7	$174.31	8.183%	$188.5738	$188.57	$188.55	$188.60
7 purchase totals =	$799.44		$864.0980	$864.09	$864.05	$864.20