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	$198.40	8.503%	$215.27	$215.27	$215.25	$215.30
Purchase #2	$25.39	12.839%	$28.6498	$28.65	$28.65	$28.60
Purchase #3	$91.72	3.813%	$95.2173	$95.22	$95.20	$95.20
Purchase #4	$204.60	5.727%	$216.3174	$216.32	$216.30	$216.30
Purchase #5	$225.96	13.398%	$256.2341	$256.23	$256.25	$256.20
Purchase #6	$124.52	5.412%	$131.259	$131.26	$131.25	$131.30
Purchase #7	$37.95	8.690%	$41.2479	$41.25	$41.25	$41.20
7 purchase totals =	$908.54		$984.1955	$984.20	$984.15	$984.10