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	$179.37	10.727%	$198.611	$198.61	$198.60	$198.60
Purchase #2	$39.91	4.526%	$41.7163	$41.72	$41.70	$41.70
Purchase #3	$141.40	7.385%	$151.8424	$151.84	$151.85	$151.80
Purchase #4	$202.61	9.838%	$222.5428	$222.54	$222.55	$222.50
Purchase #5	$63.62	6.425%	$67.7076	$67.71	$67.70	$67.70
Purchase #6	$104.74	13.251%	$118.6191	$118.62	$118.60	$118.60
Purchase #7	$70.74	5.400%	$74.56	$74.56	$74.55	$74.60
7 purchase totals =	$802.39		$875.5992	$875.60	$875.55	$875.50