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	$249.26	10.782%	$276.1352	$276.14	$276.15	$276.10
Purchase #2	$33.30	4.444%	$34.7799	$34.78	$34.80	$34.80
Purchase #3	$114.99	5.415%	$121.2167	$121.22	$121.20	$121.20
Purchase #4	$179.84	9.464%	$196.8601	$196.86	$196.85	$196.90
Purchase #5	$90.86	4.431%	$94.886	$94.89	$94.90	$94.90
Purchase #6	$203.69	11.563%	$227.2427	$227.24	$227.25	$227.20
Purchase #7	$53.27	11.871%	$59.5937	$59.59	$59.60	$59.60
7 purchase totals =	$925.21		$1,010.7143	$1,010.72	$1,010.75	$1,010.70