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	$94.48	8.552%	$102.5599	$102.56	$102.55	$102.60
Purchase #2	$234.42	9.557%	$256.8235	$256.82	$256.80	$256.80
Purchase #3	$244.98	7.654%	$263.7308	$263.73	$263.75	$263.70
Purchase #4	$57.51	12.305%	$64.5866	$64.59	$64.60	$64.60
Purchase #5	$200.72	12.861%	$226.5346	$226.53	$226.55	$226.50
Purchase #6	$250.41	11.338%	$278.8015	$278.80	$278.80	$278.80
Purchase #7	$67.25	5.369%	$70.8607	$70.86	$70.85	$70.90
7 purchase totals =	$1,149.77		$1,263.8976	$1,263.89	$1,263.90	$1,263.90