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	$59.79	9.425%	$65.4252	$65.43	$65.45	$65.40
Purchase #2	$152.33	10.661%	$168.5699	$168.57	$168.55	$168.60
Purchase #3	$180.34	8.259%	$195.2343	$195.23	$195.25	$195.20
Purchase #4	$170.66	5.146%	$179.4422	$179.44	$179.45	$179.40
Purchase #5	$55.53	6.770%	$59.2894	$59.29	$59.30	$59.30
Purchase #6	$176.54	12.776%	$199.0948	$199.09	$199.10	$199.10
Purchase #7	$172.96	13.647%	$196.5639	$196.56	$196.55	$196.60
7 purchase totals =	$968.15		$1,063.6197	$1,063.61	$1,063.65	$1,063.60