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	$213.50	10.683%	$236.3082	$236.31	$236.30	$236.30
Purchase #2	$49.33	9.346%	$53.9404	$53.94	$53.95	$53.90
Purchase #3	$173.53	11.802%	$194.01	$194.01	$194.00	$194.00
Purchase #4	$226.91	11.735%	$253.5379	$253.54	$253.55	$253.50
Purchase #5	$190.30	11.671%	$212.5099	$212.51	$212.50	$212.50
Purchase #6	$151.33	4.655%	$158.3744	$158.37	$158.35	$158.40
Purchase #7	$143.72	4.850%	$150.6904	$150.69	$150.70	$150.70
7 purchase totals =	$1,148.62		$1,259.3712	$1,259.37	$1,259.35	$1,259.30