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	$166.52	13.652%	$189.2533	$189.25	$189.25	$189.30
Purchase #2	$124.31	10.467%	$137.3215	$137.32	$137.30	$137.30
Purchase #3	$179.74	3.149%	$185.4	$185.40	$185.40	$185.40
Purchase #4	$94.30	5.701%	$99.676	$99.68	$99.70	$99.70
Purchase #5	$50.48	8.183%	$54.6108	$54.61	$54.60	$54.60
Purchase #6	$224.27	7.537%	$241.1732	$241.17	$241.15	$241.20
Purchase #7	$145.49	7.414%	$156.2766	$156.28	$156.30	$156.30
7 purchase totals =	$985.11		$1,063.7114	$1,063.71	$1,063.70	$1,063.80