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	$148.27	11.131%	$164.7739	$164.77	$164.75	$164.80
Purchase #2	$39.51	7.253%	$42.3757	$42.38	$42.40	$42.40
Purchase #3	$7.26	3.347%	$7.503	$7.50	$7.50	$7.50
Purchase #4	$149.65	11.871%	$167.415	$167.42	$167.40	$167.40
Purchase #5	$108.49	13.291%	$122.9094	$122.91	$122.90	$122.90
Purchase #6	$172.34	7.375%	$185.0501	$185.05	$185.05	$185.10
Purchase #7	$153.81	8.286%	$166.5547	$166.55	$166.55	$166.60
7 purchase totals =	$779.33		$856.5818	$856.58	$856.55	$856.70