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	$167.64	10.624%	$185.4501	$185.45	$185.45	$185.50
Purchase #2	$29.43	3.345%	$30.4144	$30.41	$30.40	$30.40
Purchase #3	$189.63	13.119%	$214.5076	$214.51	$214.50	$214.50
Purchase #4	$44.42	10.819%	$49.2258	$49.23	$49.25	$49.20
Purchase #5	$83.28	3.715%	$86.3739	$86.37	$86.35	$86.40
Purchase #6	$92.59	11.406%	$103.1508	$103.15	$103.15	$103.20
Purchase #7	$199.91	11.752%	$223.4034	$223.40	$223.40	$223.40
7 purchase totals =	$806.90		$892.5260	$892.52	$892.50	$892.60