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	$187.90	12.199%	$210.8219	$210.82	$210.80	$210.80
Purchase #2	$148.75	6.499%	$158.4173	$158.42	$158.40	$158.40
Purchase #3	$56.88	4.414%	$59.3907	$59.39	$59.40	$59.40
Purchase #4	$102.37	8.433%	$111.0029	$111.00	$111.00	$111.00
Purchase #5	$127.62	5.283%	$134.3622	$134.36	$134.35	$134.40
Purchase #6	$121.40	7.368%	$130.3448	$130.34	$130.35	$130.30
Purchase #7	$192.30	10.281%	$212.0704	$212.07	$212.05	$212.10
7 purchase totals =	$937.22		$1,016.4102	$1,016.40	$1,016.35	$1,016.40