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	$61.27	6.367%	$65.1711	$65.17	$65.15	$65.20
Purchase #2	$200.36	11.207%	$222.8143	$222.81	$222.80	$222.80
Purchase #3	$96.60	7.366%	$103.7156	$103.72	$103.70	$103.70
Purchase #4	$174.71	5.645%	$184.5724	$184.57	$184.55	$184.60
Purchase #5	$55.76	7.523%	$59.9548	$59.95	$59.95	$60.00
Purchase #6	$50.38	8.301%	$54.562	$54.56	$54.55	$54.60
Purchase #7	$174.62	4.573%	$182.6054	$182.61	$182.60	$182.60
7 purchase totals =	$813.70		$873.3956	$873.39	$873.30	$873.50