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	$89.79	5.382%	$94.6225	$94.62	$94.60	$94.60
Purchase #2	$86.39	10.388%	$95.3642	$95.36	$95.35	$95.40
Purchase #3	$200.56	11.445%	$223.5141	$223.51	$223.50	$223.50
Purchase #4	$85.89	12.223%	$96.3883	$96.39	$96.40	$96.40
Purchase #5	$236.31	11.537%	$263.5731	$263.57	$263.55	$263.60
Purchase #6	$69.85	11.528%	$77.9023	$77.90	$77.90	$77.90
Purchase #7	$88.95	8.711%	$96.6984	$96.70	$96.70	$96.70
7 purchase totals =	$857.74		$948.0629	$948.05	$948.00	$948.10