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	$109.34	12.527%	$123.037	$123.04	$123.05	$123.00
Purchase #2	$54.54	6.410%	$58.036	$58.04	$58.05	$58.00
Purchase #3	$57.82	4.790%	$60.5896	$60.59	$60.60	$60.60
Purchase #4	$37.63	13.656%	$42.7688	$42.77	$42.75	$42.80
Purchase #5	$232.33	10.648%	$257.0685	$257.07	$257.05	$257.10
Purchase #6	$100.42	7.360%	$107.8109	$107.81	$107.80	$107.80
Purchase #7	$133.86	10.229%	$147.5525	$147.55	$147.55	$147.60
7 purchase totals =	$725.94		$796.8633	$796.87	$796.85	$796.90