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	$136.57	11.190%	$151.8522	$151.85	$151.85	$151.90
Purchase #2	$130.41	13.794%	$148.3988	$148.40	$148.40	$148.40
Purchase #3	$41.64	13.274%	$47.1673	$47.17	$47.15	$47.20
Purchase #4	$183.57	3.357%	$189.7324	$189.73	$189.75	$189.70
Purchase #5	$104.50	13.531%	$118.6399	$118.64	$118.65	$118.60
Purchase #6	$179.83	11.644%	$200.7694	$200.77	$200.75	$200.80
Purchase #7	$42.97	5.244%	$45.2233	$45.22	$45.20	$45.20
7 purchase totals =	$819.49		$901.7833	$901.78	$901.75	$901.80