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	$233.33	5.852%	$246.9845	$246.98	$247.00	$247.00
Purchase #2	$75.38	10.520%	$83.31	$83.31	$83.30	$83.30
Purchase #3	$162.85	13.413%	$184.6931	$184.69	$184.70	$184.70
Purchase #4	$247.87	4.655%	$259.4083	$259.41	$259.40	$259.40
Purchase #5	$40.51	5.665%	$42.8049	$42.80	$42.80	$42.80
Purchase #6	$212.30	7.796%	$228.8509	$228.85	$228.85	$228.90
Purchase #7	$165.93	4.512%	$173.4168	$173.42	$173.40	$173.40
7 purchase totals =	$1,138.17		$1,219.4685	$1,219.46	$1,219.45	$1,219.50