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	$65.42	7.808%	$70.528	$70.53	$70.55	$70.50
Purchase #2	$95.84	10.126%	$105.5448	$105.54	$105.55	$105.50
Purchase #3	$128.31	6.391%	$136.5103	$136.51	$136.50	$136.50
Purchase #4	$46.59	12.660%	$52.4883	$52.49	$52.50	$52.50
Purchase #5	$242.52	12.684%	$273.2812	$273.28	$273.30	$273.30
Purchase #6	$228.45	11.263%	$254.1803	$254.18	$254.20	$254.20
Purchase #7	$247.95	13.628%	$281.7406	$281.74	$281.75	$281.70
7 purchase totals =	$1,055.08		$1,174.2735	$1,174.27	$1,174.35	$1,174.20