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	$216.48	4.132%	$225.425	$225.43	$225.45	$225.40
Purchase #2	$43.81	4.220%	$45.6588	$45.66	$45.65	$45.70
Purchase #3	$137.33	4.226%	$143.1336	$143.13	$143.15	$143.10
Purchase #4	$85.48	9.143%	$93.2954	$93.30	$93.30	$93.30
Purchase #5	$51.65	5.447%	$54.4634	$54.46	$54.45	$54.50
Purchase #6	$57.79	8.288%	$62.5796	$62.58	$62.60	$62.60
Purchase #7	$155.38	7.193%	$166.5565	$166.56	$166.55	$166.60
7 purchase totals =	$747.92		$791.1123	$791.12	$791.15	$791.20