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	$86.38	11.769%	$96.5461	$96.55	$96.55	$96.50
Purchase #2	$181.45	7.694%	$195.4108	$195.41	$195.40	$195.40
Purchase #3	$212.40	4.466%	$221.8858	$221.89	$221.90	$221.90
Purchase #4	$62.52	5.159%	$65.7454	$65.75	$65.75	$65.70
Purchase #5	$21.80	7.269%	$23.3846	$23.38	$23.40	$23.40
Purchase #6	$91.57	9.760%	$100.5072	$100.51	$100.50	$100.50
Purchase #7	$153.47	10.463%	$169.5276	$169.53	$169.55	$169.50
7 purchase totals =	$809.59		$873.0075	$873.02	$873.05	$872.90