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	$89.33	12.554%	$100.5445	$100.54	$100.55	$100.50
Purchase #2	$216.33	3.645%	$224.2152	$224.22	$224.20	$224.20
Purchase #3	$52.70	12.555%	$59.3165	$59.32	$59.30	$59.30
Purchase #4	$81.81	11.660%	$91.349	$91.35	$91.35	$91.30
Purchase #5	$197.33	10.857%	$218.7541	$218.75	$218.75	$218.80
Purchase #6	$174.67	13.598%	$198.4216	$198.42	$198.40	$198.40
Purchase #7	$180.44	13.625%	$205.025	$205.03	$205.05	$205.00
7 purchase totals =	$992.61		$1,097.6259	$1,097.63	$1,097.60	$1,097.50