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	$222.37	3.121%	$229.3102	$229.31	$229.30	$229.30
Purchase #2	$206.79	5.745%	$218.6701	$218.67	$218.65	$218.70
Purchase #3	$61.49	5.208%	$64.6924	$64.69	$64.70	$64.70
Purchase #4	$104.87	4.260%	$109.3375	$109.34	$109.35	$109.30
Purchase #5	$120.42	6.674%	$128.4568	$128.46	$128.45	$128.50
Purchase #6	$9.32	8.193%	$10.0836	$10.08	$10.10	$10.10
Purchase #7	$171.78	4.682%	$179.8227	$179.82	$179.80	$179.80
7 purchase totals =	$897.04		$940.3733	$940.37	$940.35	$940.40