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	$81.96	9.147%	$89.4569	$89.46	$89.45	$89.50
Purchase #2	$126.32	11.866%	$141.3091	$141.31	$141.30	$141.30
Purchase #3	$90.47	6.330%	$96.1968	$96.20	$96.20	$96.20
Purchase #4	$179.87	7.590%	$193.5221	$193.52	$193.50	$193.50
Purchase #5	$157.54	5.635%	$166.4174	$166.42	$166.40	$166.40
Purchase #6	$156.61	10.634%	$173.2639	$173.26	$173.25	$173.30
Purchase #7	$209.27	6.156%	$222.1527	$222.15	$222.15	$222.20
7 purchase totals =	$1,002.04		$1,082.3189	$1,082.32	$1,082.25	$1,082.40