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	$238.46	6.161%	$253.1515	$253.15	$253.15	$253.20
Purchase #2	$196.55	6.519%	$209.3631	$209.36	$209.35	$209.40
Purchase #3	$173.86	6.538%	$185.227	$185.23	$185.25	$185.20
Purchase #4	$70.74	3.618%	$73.2994	$73.30	$73.30	$73.30
Purchase #5	$53.36	6.327%	$56.7361	$56.74	$56.75	$56.70
Purchase #6	$233.48	10.746%	$258.5698	$258.57	$258.55	$258.60
Purchase #7	$43.43	4.172%	$45.2419	$45.24	$45.25	$45.20
7 purchase totals =	$1,009.88		$1,081.5888	$1,081.59	$1,081.60	$1,081.60