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	$102.89	9.203%	$112.359	$112.36	$112.35	$112.40
Purchase #2	$146.98	3.274%	$151.7921	$151.79	$151.80	$151.80
Purchase #3	$244.45	4.849%	$256.3034	$256.30	$256.30	$256.30
Purchase #4	$102.73	13.241%	$116.3325	$116.33	$116.35	$116.30
Purchase #5	$142.54	5.405%	$150.2443	$150.24	$150.25	$150.20
Purchase #6	$237.43	5.489%	$250.4625	$250.46	$250.45	$250.50
Purchase #7	$20.52	10.607%	$22.6966	$22.70	$22.70	$22.70
7 purchase totals =	$997.54		$1,060.1904	$1,060.18	$1,060.20	$1,060.20