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	$62.70	7.538%	$67.4263	$67.43	$67.45	$67.40
Purchase #2	$25.58	9.687%	$28.0579	$28.06	$28.05	$28.10
Purchase #3	$216.45	13.599%	$245.885	$245.89	$245.90	$245.90
Purchase #4	$235.47	7.655%	$253.4952	$253.50	$253.50	$253.50
Purchase #5	$192.73	13.546%	$218.8372	$218.84	$218.85	$218.80
Purchase #6	$244.73	10.796%	$271.1511	$271.15	$271.15	$271.20
Purchase #7	$95.63	11.746%	$106.8627	$106.86	$106.85	$106.90
7 purchase totals =	$1,073.29		$1,191.7154	$1,191.73	$1,191.75	$1,191.80