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	$212.34	6.306%	$225.7302	$225.73	$225.75	$225.70
Purchase #2	$170.79	10.159%	$188.1406	$188.14	$188.15	$188.10
Purchase #3	$44.86	12.160%	$50.315	$50.32	$50.30	$50.30
Purchase #4	$125.84	8.173%	$136.1249	$136.12	$136.10	$136.10
Purchase #5	$166.48	3.108%	$171.6542	$171.65	$171.65	$171.70
Purchase #6	$131.69	5.833%	$139.3715	$139.37	$139.35	$139.40
Purchase #7	$158.69	13.764%	$180.5321	$180.53	$180.55	$180.50
7 purchase totals =	$1,010.69		$1,091.8685	$1,091.86	$1,091.85	$1,091.80