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	$143.89	11.350%	$160.2215	$160.22	$160.20	$160.20
Purchase #2	$20.47	8.739%	$22.2589	$22.26	$22.25	$22.30
Purchase #3	$247.98	13.464%	$281.368	$281.37	$281.35	$281.40
Purchase #4	$182.89	7.645%	$196.8719	$196.87	$196.85	$196.90
Purchase #5	$86.70	6.432%	$92.2765	$92.28	$92.30	$92.30
Purchase #6	$122.57	3.802%	$127.2301	$127.23	$127.25	$127.20
Purchase #7	$151.38	11.760%	$169.1823	$169.18	$169.20	$169.20
7 purchase totals =	$955.88		$1,049.4092	$1,049.41	$1,049.40	$1,049.50