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	$176.75	5.562%	$186.5808	$186.58	$186.60	$186.60
Purchase #2	$49.91	7.763%	$53.7845	$53.78	$53.80	$53.80
Purchase #3	$111.88	11.167%	$124.3736	$124.37	$124.35	$124.40
Purchase #4	$25.40	11.220%	$28.2499	$28.25	$28.25	$28.20
Purchase #5	$28.70	9.399%	$31.3975	$31.40	$31.40	$31.40
Purchase #6	$52.92	12.130%	$59.3392	$59.34	$59.35	$59.30
Purchase #7	$199.63	11.430%	$222.4477	$222.45	$222.45	$222.40
7 purchase totals =	$645.19		$706.1732	$706.17	$706.20	$706.10