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	$179.88	9.250%	$196.5189	$196.52	$196.50	$196.50
Purchase #2	$247.44	9.638%	$271.2883	$271.29	$271.30	$271.30
Purchase #3	$200.89	11.367%	$223.7252	$223.73	$223.75	$223.70
Purchase #4	$235.49	6.298%	$250.3212	$250.32	$250.30	$250.30
Purchase #5	$233.47	5.154%	$245.503	$245.50	$245.50	$245.50
Purchase #6	$205.58	6.253%	$218.4349	$218.43	$218.45	$218.40
Purchase #7	$96.60	6.405%	$102.7872	$102.79	$102.80	$102.80
7 purchase totals =	$1,399.35		$1,508.5787	$1,508.58	$1,508.60	$1,508.50