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	$179.98	4.696%	$188.4319	$188.43	$188.45	$188.40
Purchase #2	$92.81	13.791%	$105.6094	$105.61	$105.60	$105.60
Purchase #3	$131.49	3.539%	$136.1434	$136.14	$136.15	$136.10
Purchase #4	$224.61	13.856%	$255.732	$255.73	$255.75	$255.70
Purchase #5	$93.96	9.153%	$102.5602	$102.56	$102.55	$102.60
Purchase #6	$165.81	6.385%	$176.397	$176.40	$176.40	$176.40
Purchase #7	$211.45	6.309%	$224.7904	$224.79	$224.80	$224.80
7 purchase totals =	$1,100.11		$1,189.6643	$1,189.66	$1,189.70	$1,189.60