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	$173.27	9.473%	$189.6839	$189.68	$189.70	$189.70
Purchase #2	$102.39	8.666%	$111.2631	$111.26	$111.25	$111.30
Purchase #3	$187.65	11.129%	$208.5336	$208.53	$208.55	$208.50
Purchase #4	$148.71	7.124%	$159.3041	$159.30	$159.30	$159.30
Purchase #5	$235.77	3.742%	$244.5925	$244.59	$244.60	$244.60
Purchase #6	$31.70	5.611%	$33.4787	$33.48	$33.50	$33.50
Purchase #7	$170.62	8.441%	$185.022	$185.02	$185.00	$185.00
7 purchase totals =	$1,050.11		$1,131.8779	$1,131.86	$1,131.90	$1,131.90