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	$232.48	11.727%	$259.7429	$259.74	$259.75	$259.70
Purchase #2	$137.47	6.827%	$146.8551	$146.86	$146.85	$146.90
Purchase #3	$81.80	9.832%	$89.8426	$89.84	$89.85	$89.80
Purchase #4	$232.86	8.814%	$253.3843	$253.38	$253.40	$253.40
Purchase #5	$95.94	7.420%	$103.0587	$103.06	$103.05	$103.10
Purchase #6	$91.43	4.627%	$95.6605	$95.66	$95.65	$95.70
Purchase #7	$248.75	5.512%	$262.4611	$262.46	$262.45	$262.50
7 purchase totals =	$1,120.73		$1,211.0052	$1,211.00	$1,211.00	$1,211.10