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	$227.92	7.146%	$244.2072	$244.21	$244.20	$244.20
Purchase #2	$194.44	10.825%	$215.4881	$215.49	$215.50	$215.50
Purchase #3	$155.72	9.872%	$171.0927	$171.09	$171.10	$171.10
Purchase #4	$101.62	5.131%	$106.8341	$106.83	$106.85	$106.80
Purchase #5	$105.83	5.688%	$111.8496	$111.85	$111.85	$111.80
Purchase #6	$51.30	8.754%	$55.7908	$55.79	$55.80	$55.80
Purchase #7	$101.49	4.301%	$105.8551	$105.86	$105.85	$105.90
7 purchase totals =	$938.32		$1,011.1176	$1,011.12	$1,011.15	$1,011.10