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	$109.76	6.527%	$116.924	$116.92	$116.90	$116.90
Purchase #2	$128.38	4.558%	$134.2316	$134.23	$134.25	$134.20
Purchase #3	$200.89	11.685%	$224.364	$224.36	$224.35	$224.40
Purchase #4	$161.60	11.748%	$180.5848	$180.58	$180.60	$180.60
Purchase #5	$64.72	11.586%	$72.2185	$72.22	$72.20	$72.20
Purchase #6	$124.39	13.651%	$141.3705	$141.37	$141.35	$141.40
Purchase #7	$213.79	8.279%	$231.4897	$231.49	$231.50	$231.50
7 purchase totals =	$1,003.53		$1,101.1831	$1,101.17	$1,101.15	$1,101.20