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	$194.57	7.579%	$209.3165	$209.32	$209.30	$209.30
Purchase #2	$53.39	11.469%	$59.5133	$59.51	$59.50	$59.50
Purchase #3	$197.40	11.699%	$220.4938	$220.49	$220.50	$220.50
Purchase #4	$90.43	11.820%	$101.1188	$101.12	$101.10	$101.10
Purchase #5	$94.78	7.390%	$101.7842	$101.78	$101.80	$101.80
Purchase #6	$180.86	10.330%	$199.5428	$199.54	$199.55	$199.50
Purchase #7	$243.72	13.790%	$277.329	$277.33	$277.35	$277.30
7 purchase totals =	$1,055.15		$1,169.0984	$1,169.09	$1,169.10	$1,169.00