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	$45.28	3.276%	$46.7634	$46.76	$46.75	$46.80
Purchase #2	$84.37	6.743%	$90.0591	$90.06	$90.05	$90.10
Purchase #3	$165.87	11.645%	$185.1856	$185.19	$185.20	$185.20
Purchase #4	$6.79	5.681%	$7.1757	$7.18	$7.20	$7.20
Purchase #5	$248.97	6.321%	$264.7074	$264.71	$264.70	$264.70
Purchase #6	$6.61	6.647%	$7.0494	$7.05	$7.05	$7.00
Purchase #7	$192.53	4.199%	$200.6143	$200.61	$200.60	$200.60
7 purchase totals =	$750.42		$801.5549	$801.56	$801.55	$801.60