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	$83.43	12.594%	$93.9372	$93.94	$93.95	$93.90
Purchase #2	$43.38	7.533%	$46.6478	$46.65	$46.65	$46.60
Purchase #3	$35.43	13.507%	$40.2155	$40.22	$40.20	$40.20
Purchase #4	$111.32	10.529%	$123.0409	$123.04	$123.05	$123.00
Purchase #5	$234.27	12.385%	$263.2843	$263.28	$263.30	$263.30
Purchase #6	$36.95	10.830%	$40.9517	$40.95	$40.95	$41.00
Purchase #7	$41.76	11.604%	$46.6058	$46.61	$46.60	$46.60
7 purchase totals =	$586.54		$654.6832	$654.69	$654.70	$654.60