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	$219.50	11.817%	$245.4383	$245.44	$245.45	$245.40
Purchase #2	$91.72	13.439%	$104.0463	$104.05	$104.05	$104.00
Purchase #3	$123.49	6.705%	$131.77	$131.77	$131.75	$131.80
Purchase #4	$216.85	12.301%	$243.5247	$243.52	$243.50	$243.50
Purchase #5	$237.85	7.616%	$255.9647	$255.96	$255.95	$256.00
Purchase #6	$151.44	6.230%	$160.8747	$160.87	$160.85	$160.90
Purchase #7	$244.54	9.443%	$267.6319	$267.63	$267.65	$267.60
7 purchase totals =	$1,285.39		$1,409.2506	$1,409.24	$1,409.20	$1,409.20