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	$59.53	7.143%	$63.7822	$63.78	$63.80	$63.80
Purchase #2	$162.44	6.403%	$172.841	$172.84	$172.85	$172.80
Purchase #3	$123.30	8.192%	$133.4007	$133.40	$133.40	$133.40
Purchase #4	$162.43	4.275%	$169.3739	$169.37	$169.35	$169.40
Purchase #5	$50.75	7.315%	$54.4624	$54.46	$54.45	$54.50
Purchase #6	$250.97	7.800%	$270.5457	$270.55	$270.55	$270.50
Purchase #7	$157.80	9.596%	$172.9425	$172.94	$172.95	$172.90
7 purchase totals =	$967.22		$1,037.3484	$1,037.34	$1,037.35	$1,037.30