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	$144.41	11.147%	$160.5074	$160.51	$160.50	$160.50
Purchase #2	$13.46	10.404%	$14.8604	$14.86	$14.85	$14.90
Purchase #3	$133.30	10.825%	$147.7297	$147.73	$147.75	$147.70
Purchase #4	$67.49	7.177%	$72.3338	$72.33	$72.35	$72.30
Purchase #5	$53.76	4.273%	$56.0572	$56.06	$56.05	$56.10
Purchase #6	$43.31	11.584%	$48.327	$48.33	$48.35	$48.30
Purchase #7	$138.96	10.720%	$153.8565	$153.86	$153.85	$153.90
7 purchase totals =	$594.69		$653.6720	$653.68	$653.70	$653.70