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	$113.54	8.821%	$123.5554	$123.56	$123.55	$123.60
Purchase #2	$62.29	4.603%	$65.1572	$65.16	$65.15	$65.20
Purchase #3	$193.84	11.351%	$215.8428	$215.84	$215.85	$215.80
Purchase #4	$238.73	12.639%	$268.9031	$268.90	$268.90	$268.90
Purchase #5	$193.61	6.218%	$205.6487	$205.65	$205.65	$205.60
Purchase #6	$43.90	9.649%	$48.1359	$48.14	$48.15	$48.10
Purchase #7	$168.40	10.137%	$185.4707	$185.47	$185.45	$185.50
7 purchase totals =	$1,014.31		$1,112.7138	$1,112.72	$1,112.70	$1,112.70