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	$111.29	5.540%	$117.4555	$117.46	$117.45	$117.50
Purchase #2	$191.70	12.187%	$215.0625	$215.06	$215.05	$215.10
Purchase #3	$29.86	3.851%	$31.0099	$31.01	$31.00	$31.00
Purchase #4	$103.78	13.546%	$117.838	$117.84	$117.85	$117.80
Purchase #5	$250.42	7.507%	$269.219	$269.22	$269.20	$269.20
Purchase #6	$121.98	4.259%	$127.1751	$127.18	$127.20	$127.20
Purchase #7	$154.35	8.624%	$167.6611	$167.66	$167.65	$167.70
7 purchase totals =	$963.38		$1,045.4211	$1,045.43	$1,045.40	$1,045.50