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	$168.47	4.342%	$175.785	$175.79	$175.80	$175.80
Purchase #2	$228.51	6.145%	$242.5519	$242.55	$242.55	$242.60
Purchase #3	$155.84	12.522%	$175.3543	$175.35	$175.35	$175.40
Purchase #4	$194.58	10.730%	$215.4584	$215.46	$215.45	$215.50
Purchase #5	$125.70	13.663%	$142.8744	$142.87	$142.85	$142.90
Purchase #6	$100.77	5.748%	$106.5623	$106.56	$106.55	$106.60
Purchase #7	$29.71	10.567%	$32.8495	$32.85	$32.85	$32.80
7 purchase totals =	$1,003.58		$1,091.4358	$1,091.43	$1,091.40	$1,091.60