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	$164.82	6.715%	$175.8877	$175.89	$175.90	$175.90
Purchase #2	$5.61	4.472%	$5.8609	$5.86	$5.85	$5.90
Purchase #3	$141.74	13.186%	$160.4298	$160.43	$160.45	$160.40
Purchase #4	$218.36	3.184%	$225.3126	$225.31	$225.30	$225.30
Purchase #5	$200.56	12.456%	$225.5418	$225.54	$225.55	$225.50
Purchase #6	$121.76	13.121%	$137.7361	$137.74	$137.75	$137.70
Purchase #7	$83.62	7.583%	$89.9609	$89.96	$89.95	$90.00
7 purchase totals =	$936.47		$1,020.7298	$1,020.73	$1,020.75	$1,020.70