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	$63.33	7.226%	$67.9062	$67.91	$67.90	$67.90
Purchase #2	$244.87	10.689%	$271.0442	$271.04	$271.05	$271.00
Purchase #3	$129.74	9.471%	$142.0277	$142.03	$142.05	$142.00
Purchase #4	$172.74	4.515%	$180.5392	$180.54	$180.55	$180.50
Purchase #5	$231.83	10.474%	$256.1119	$256.11	$256.10	$256.10
Purchase #6	$82.61	9.589%	$90.5315	$90.53	$90.55	$90.50
Purchase #7	$10.90	5.802%	$11.5324	$11.53	$11.55	$11.50
7 purchase totals =	$936.02		$1,019.6931	$1,019.69	$1,019.75	$1,019.50