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	$114.92	13.716%	$130.6824	$130.68	$130.70	$130.70
Purchase #2	$106.74	7.219%	$114.4456	$114.45	$114.45	$114.40
Purchase #3	$196.52	9.569%	$215.325	$215.33	$215.35	$215.30
Purchase #4	$222.61	8.839%	$242.2865	$242.29	$242.30	$242.30
Purchase #5	$50.41	7.784%	$54.3339	$54.33	$54.35	$54.30
Purchase #6	$35.95	9.345%	$39.3095	$39.31	$39.30	$39.30
Purchase #7	$194.58	3.217%	$200.8396	$200.84	$200.85	$200.80
7 purchase totals =	$921.73		$997.2225	$997.23	$997.30	$997.10