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	$57.28	7.760%	$61.7249	$61.72	$61.70	$61.70
Purchase #2	$239.54	4.850%	$251.1577	$251.16	$251.15	$251.20
Purchase #3	$103.72	11.273%	$115.4124	$115.41	$115.40	$115.40
Purchase #4	$235.71	8.275%	$255.215	$255.22	$255.20	$255.20
Purchase #5	$103.84	8.413%	$112.5761	$112.58	$112.60	$112.60
Purchase #6	$67.80	6.592%	$72.2694	$72.27	$72.25	$72.30
Purchase #7	$157.87	10.768%	$174.8694	$174.87	$174.85	$174.90
7 purchase totals =	$965.76		$1,043.2249	$1,043.23	$1,043.15	$1,043.30