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	$41.91	8.464%	$45.4573	$45.46	$45.45	$45.50
Purchase #2	$81.25	3.487%	$84.0832	$84.08	$84.10	$84.10
Purchase #3	$148.84	10.279%	$164.1393	$164.14	$164.15	$164.10
Purchase #4	$146.94	3.160%	$151.5833	$151.58	$151.60	$151.60
Purchase #5	$119.27	3.757%	$123.751	$123.75	$123.75	$123.80
Purchase #6	$42.52	7.586%	$45.7456	$45.75	$45.75	$45.70
Purchase #7	$211.90	3.496%	$219.308	$219.31	$219.30	$219.30
7 purchase totals =	$792.63		$834.0677	$834.07	$834.10	$834.10