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	$225.84	3.397%	$233.5118	$233.51	$233.50	$233.50
Purchase #2	$92.39	4.837%	$96.8589	$96.86	$96.85	$96.90
Purchase #3	$220.51	13.669%	$250.6515	$250.65	$250.65	$250.70
Purchase #4	$32.71	6.495%	$34.8345	$34.83	$34.85	$34.80
Purchase #5	$95.80	9.563%	$104.9614	$104.96	$104.95	$105.00
Purchase #6	$202.89	4.700%	$212.4258	$212.43	$212.45	$212.40
Purchase #7	$68.84	12.699%	$77.582	$77.58	$77.60	$77.60
7 purchase totals =	$938.98		$1,010.8259	$1,010.82	$1,010.85	$1,010.90