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	$141.81	7.271%	$152.121	$152.12	$152.10	$152.10
Purchase #2	$13.42	4.737%	$14.0557	$14.06	$14.05	$14.10
Purchase #3	$73.69	12.442%	$82.8585	$82.86	$82.85	$82.90
Purchase #4	$13.39	8.676%	$14.5517	$14.55	$14.55	$14.60
Purchase #5	$93.82	10.681%	$103.8409	$103.84	$103.85	$103.80
Purchase #6	$25.68	5.657%	$27.1327	$27.13	$27.15	$27.10
Purchase #7	$84.70	9.286%	$92.5652	$92.57	$92.55	$92.60
7 purchase totals =	$446.51		$487.1257	$487.13	$487.10	$487.20