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	$67.46	10.263%	$74.3834	$74.38	$74.40	$74.40
Purchase #2	$61.85	6.550%	$65.9012	$65.90	$65.90	$65.90
Purchase #3	$134.59	9.110%	$146.8511	$146.85	$146.85	$146.90
Purchase #4	$148.96	7.593%	$160.2705	$160.27	$160.25	$160.30
Purchase #5	$218.53	13.533%	$248.1037	$248.10	$248.10	$248.10
Purchase #6	$121.73	4.547%	$127.2651	$127.27	$127.25	$127.30
Purchase #7	$231.39	6.762%	$247.0366	$247.04	$247.05	$247.00
7 purchase totals =	$984.51		$1,069.8116	$1,069.81	$1,069.80	$1,069.90