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	$49.35	10.432%	$54.4982	$54.50	$54.50	$54.50
Purchase #2	$14.37	11.871%	$16.0759	$16.08	$16.10	$16.10
Purchase #3	$6.40	11.430%	$7.1315	$7.13	$7.15	$7.10
Purchase #4	$62.53	7.652%	$67.3148	$67.31	$67.30	$67.30
Purchase #5	$186.43	9.594%	$204.3161	$204.32	$204.30	$204.30
Purchase #6	$59.57	13.237%	$67.4553	$67.46	$67.45	$67.50
Purchase #7	$52.50	13.736%	$59.7114	$59.71	$59.70	$59.70
7 purchase totals =	$431.15		$476.5032	$476.51	$476.50	$476.50