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	$76.53	13.567%	$86.9128	$86.91	$86.90	$86.90
Purchase #2	$234.89	8.699%	$255.3231	$255.32	$255.30	$255.30
Purchase #3	$62.26	8.618%	$67.6256	$67.63	$67.65	$67.60
Purchase #4	$32.29	9.104%	$35.2297	$35.23	$35.25	$35.20
Purchase #5	$119.74	9.290%	$130.8638	$130.86	$130.85	$130.90
Purchase #6	$167.52	5.199%	$176.2294	$176.23	$176.25	$176.20
Purchase #7	$89.48	13.198%	$101.2896	$101.29	$101.30	$101.30
7 purchase totals =	$782.71		$853.4740	$853.47	$853.50	$853.40