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	$63.54	11.204%	$70.659	$70.66	$70.65	$70.70
Purchase #2	$130.89	10.316%	$144.3926	$144.39	$144.40	$144.40
Purchase #3	$232.38	7.741%	$250.3685	$250.37	$250.35	$250.40
Purchase #4	$134.88	9.652%	$147.8986	$147.90	$147.90	$147.90
Purchase #5	$77.83	6.328%	$82.7551	$82.76	$82.75	$82.80
Purchase #6	$194.77	4.223%	$202.9951	$203.00	$203.00	$203.00
Purchase #7	$60.45	11.495%	$67.3987	$67.40	$67.40	$67.40
7 purchase totals =	$894.74		$966.4676	$966.48	$966.45	$966.60