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	$127.42	4.521%	$133.1807	$133.18	$133.20	$133.20
Purchase #2	$25.82	7.603%	$27.7831	$27.78	$27.80	$27.80
Purchase #3	$167.92	11.720%	$187.6002	$187.60	$187.60	$187.60
Purchase #4	$100.65	10.791%	$111.5111	$111.51	$111.50	$111.50
Purchase #5	$170.36	13.582%	$193.4983	$193.50	$193.50	$193.50
Purchase #6	$189.34	3.679%	$196.3058	$196.31	$196.30	$196.30
Purchase #7	$76.44	12.211%	$85.7741	$85.77	$85.75	$85.80
7 purchase totals =	$857.95		$935.6533	$935.65	$935.65	$935.70