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	$67.87	6.119%	$72.023	$72.02	$72.00	$72.00
Purchase #2	$122.40	3.209%	$126.3278	$126.33	$126.35	$126.30
Purchase #3	$118.62	7.844%	$127.9246	$127.92	$127.90	$127.90
Purchase #4	$32.77	11.267%	$36.4622	$36.46	$36.45	$36.50
Purchase #5	$22.76	10.690%	$25.193	$25.19	$25.20	$25.20
Purchase #6	$182.74	7.546%	$196.5296	$196.53	$196.55	$196.50
Purchase #7	$241.81	5.587%	$255.3199	$255.32	$255.30	$255.30
7 purchase totals =	$788.97		$839.7801	$839.77	$839.75	$839.70