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	$63.70	13.128%	$72.0625	$72.06	$72.05	$72.10
Purchase #2	$37.61	13.188%	$42.57	$42.57	$42.55	$42.60
Purchase #3	$184.32	6.289%	$195.9119	$195.91	$195.90	$195.90
Purchase #4	$52.29	12.507%	$58.8299	$58.83	$58.85	$58.80
Purchase #5	$216.41	12.253%	$242.9267	$242.93	$242.95	$242.90
Purchase #6	$77.33	12.311%	$86.8501	$86.85	$86.85	$86.90
Purchase #7	$106.70	5.358%	$112.417	$112.42	$112.40	$112.40
7 purchase totals =	$738.36		$811.5681	$811.57	$811.55	$811.60