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	$116.87	9.118%	$127.5262	$127.53	$127.55	$127.50
Purchase #2	$94.96	9.336%	$103.8255	$103.83	$103.85	$103.80
Purchase #3	$188.74	10.717%	$208.9673	$208.97	$208.95	$209.00
Purchase #4	$171.32	6.394%	$182.2742	$182.27	$182.25	$182.30
Purchase #5	$62.39	3.367%	$64.4907	$64.49	$64.50	$64.50
Purchase #6	$218.69	5.260%	$230.1931	$230.19	$230.20	$230.20
Purchase #7	$78.63	13.490%	$89.2372	$89.24	$89.25	$89.20
7 purchase totals =	$931.60		$1,006.5142	$1,006.52	$1,006.55	$1,006.50