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	$67.34	4.408%	$70.3083	$70.31	$70.30	$70.30
Purchase #2	$66.89	4.594%	$69.9629	$69.96	$69.95	$70.00
Purchase #3	$65.73	11.740%	$73.4467	$73.45	$73.45	$73.40
Purchase #4	$228.87	12.404%	$257.259	$257.26	$257.25	$257.30
Purchase #5	$146.72	12.380%	$164.8839	$164.88	$164.90	$164.90
Purchase #6	$100.93	13.719%	$114.7766	$114.78	$114.80	$114.80
Purchase #7	$246.87	11.425%	$275.0749	$275.07	$275.05	$275.10
7 purchase totals =	$923.35		$1,025.7123	$1,025.71	$1,025.70	$1,025.80