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	$85.57	13.223%	$96.8849	$96.88	$96.90	$96.90
Purchase #2	$79.69	11.540%	$88.8862	$88.89	$88.90	$88.90
Purchase #3	$36.47	7.134%	$39.0718	$39.07	$39.05	$39.10
Purchase #4	$57.87	3.134%	$59.6836	$59.68	$59.70	$59.70
Purchase #5	$42.37	4.188%	$44.1445	$44.14	$44.15	$44.10
Purchase #6	$77.94	3.414%	$80.6009	$80.60	$80.60	$80.60
Purchase #7	$204.31	5.308%	$215.1548	$215.15	$215.15	$215.20
7 purchase totals =	$584.22		$624.4267	$624.41	$624.45	$624.50