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	$171.53	8.384%	$185.9111	$185.91	$185.90	$185.90
Purchase #2	$37.48	7.595%	$40.3266	$40.33	$40.35	$40.30
Purchase #3	$121.27	7.789%	$130.7157	$130.72	$130.70	$130.70
Purchase #4	$23.31	4.161%	$24.2799	$24.28	$24.30	$24.30
Purchase #5	$174.35	11.530%	$194.4526	$194.45	$194.45	$194.50
Purchase #6	$123.60	13.740%	$140.5826	$140.58	$140.60	$140.60
Purchase #7	$195.41	11.855%	$218.5759	$218.58	$218.60	$218.60
7 purchase totals =	$846.95		$934.8444	$934.85	$934.90	$934.90