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	$104.87	7.251%	$112.4741	$112.47	$112.45	$112.50
Purchase #2	$78.81	5.484%	$83.1319	$83.13	$83.15	$83.10
Purchase #3	$176.42	7.607%	$189.8403	$189.84	$189.85	$189.80
Purchase #4	$62.74	7.501%	$67.4461	$67.45	$67.45	$67.40
Purchase #5	$106.43	10.764%	$117.8861	$117.89	$117.90	$117.90
Purchase #6	$199.85	4.660%	$209.163	$209.16	$209.15	$209.20
Purchase #7	$164.58	10.190%	$181.3507	$181.35	$181.35	$181.40
7 purchase totals =	$893.70		$961.2922	$961.29	$961.30	$961.30