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	$217.26	7.275%	$233.0657	$233.07	$233.05	$233.10
Purchase #2	$116.79	11.645%	$130.3902	$130.39	$130.40	$130.40
Purchase #3	$54.60	12.681%	$61.5238	$61.52	$61.50	$61.50
Purchase #4	$180.46	4.217%	$188.07	$188.07	$188.05	$188.10
Purchase #5	$213.78	4.358%	$223.0965	$223.10	$223.10	$223.10
Purchase #6	$99.47	7.111%	$106.5433	$106.54	$106.55	$106.50
Purchase #7	$225.41	5.650%	$238.1457	$238.15	$238.15	$238.10
7 purchase totals =	$1,107.77		$1,180.8352	$1,180.84	$1,180.80	$1,180.80