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	$31.66	4.715%	$33.1528	$33.15	$33.15	$33.20
Purchase #2	$191.38	11.158%	$212.7342	$212.73	$212.75	$212.70
Purchase #3	$175.72	7.667%	$189.1925	$189.19	$189.20	$189.20
Purchase #4	$93.48	5.300%	$98.4344	$98.43	$98.45	$98.40
Purchase #5	$67.61	4.253%	$70.4855	$70.49	$70.50	$70.50
Purchase #6	$153.38	8.104%	$165.8099	$165.81	$165.80	$165.80
Purchase #7	$184.64	6.419%	$196.492	$196.49	$196.50	$196.50
7 purchase totals =	$897.87		$966.3013	$966.29	$966.35	$966.30