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	$57.60	12.552%	$64.83	$64.83	$64.85	$64.80
Purchase #2	$28.86	11.214%	$32.0964	$32.10	$32.10	$32.10
Purchase #3	$181.91	5.444%	$191.8132	$191.81	$191.80	$191.80
Purchase #4	$245.77	6.397%	$261.4919	$261.49	$261.50	$261.50
Purchase #5	$158.64	5.716%	$167.7079	$167.71	$167.70	$167.70
Purchase #6	$237.61	12.212%	$266.6269	$266.63	$266.65	$266.60
Purchase #7	$86.54	10.827%	$95.9097	$95.91	$95.90	$95.90
7 purchase totals =	$996.93		$1,080.4760	$1,080.48	$1,080.50	$1,080.40