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	$209.83	11.220%	$233.3729	$233.37	$233.35	$233.40
Purchase #2	$44.63	13.284%	$50.5586	$50.56	$50.55	$50.60
Purchase #3	$120.36	6.276%	$127.9138	$127.91	$127.90	$127.90
Purchase #4	$99.94	11.485%	$111.4181	$111.42	$111.40	$111.40
Purchase #5	$83.55	13.468%	$94.8025	$94.80	$94.80	$94.80
Purchase #6	$8.69	9.553%	$9.5202	$9.52	$9.50	$9.50
Purchase #7	$55.58	9.420%	$60.8156	$60.82	$60.80	$60.80
7 purchase totals =	$622.58		$688.4017	$688.40	$688.30	$688.40