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	$11.81	6.282%	$12.5519	$12.55	$12.55	$12.60
Purchase #2	$72.61	12.399%	$81.6129	$81.61	$81.60	$81.60
Purchase #3	$168.38	3.140%	$173.6671	$173.67	$173.65	$173.70
Purchase #4	$56.81	3.315%	$58.6933	$58.69	$58.70	$58.70
Purchase #5	$81.73	11.201%	$90.8846	$90.88	$90.90	$90.90
Purchase #6	$93.72	7.314%	$100.5747	$100.57	$100.55	$100.60
Purchase #7	$154.30	9.639%	$169.173	$169.17	$169.15	$169.20
7 purchase totals =	$639.36		$687.1575	$687.14	$687.10	$687.30