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	$209.74	13.553%	$238.1661	$238.17	$238.15	$238.20
Purchase #2	$86.49	13.642%	$98.289	$98.29	$98.30	$98.30
Purchase #3	$93.85	7.717%	$101.0924	$101.09	$101.10	$101.10
Purchase #4	$46.58	13.264%	$52.7584	$52.76	$52.75	$52.80
Purchase #5	$58.90	4.553%	$61.5817	$61.58	$61.60	$61.60
Purchase #6	$244.62	4.758%	$256.259	$256.26	$256.25	$256.30
Purchase #7	$206.33	7.852%	$222.531	$222.53	$222.55	$222.50
7 purchase totals =	$946.51		$1,030.6776	$1,030.68	$1,030.70	$1,030.80