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	$188.46	12.219%	$211.4879	$211.49	$211.50	$211.50
Purchase #2	$147.68	3.381%	$152.6731	$152.67	$152.65	$152.70
Purchase #3	$201.77	3.785%	$209.407	$209.41	$209.40	$209.40
Purchase #4	$83.82	7.838%	$90.3898	$90.39	$90.40	$90.40
Purchase #5	$235.86	12.251%	$264.7552	$264.76	$264.75	$264.80
Purchase #6	$136.38	13.561%	$154.8745	$154.87	$154.85	$154.90
Purchase #7	$126.47	3.849%	$131.3378	$131.34	$131.35	$131.30
7 purchase totals =	$1,120.44		$1,214.9253	$1,214.93	$1,214.90	$1,215.00