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	$151.58	7.187%	$162.4741	$162.47	$162.45	$162.50
Purchase #2	$147.64	13.686%	$167.846	$167.85	$167.85	$167.80
Purchase #3	$179.43	3.250%	$185.2615	$185.26	$185.25	$185.30
Purchase #4	$196.28	4.485%	$205.0832	$205.08	$205.10	$205.10
Purchase #5	$121.99	9.485%	$133.5608	$133.56	$133.55	$133.60
Purchase #6	$122.45	7.647%	$131.8138	$131.81	$131.80	$131.80
Purchase #7	$245.98	9.770%	$270.0122	$270.01	$270.00	$270.00
7 purchase totals =	$1,165.35		$1,256.0516	$1,256.04	$1,256.00	$1,256.10