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	$134.85	7.292%	$144.6833	$144.68	$144.70	$144.70
Purchase #2	$42.39	7.172%	$45.4302	$45.43	$45.45	$45.40
Purchase #3	$218.73	4.175%	$227.862	$227.86	$227.85	$227.90
Purchase #4	$37.99	3.289%	$39.2395	$39.24	$39.25	$39.20
Purchase #5	$220.37	7.118%	$236.0559	$236.06	$236.05	$236.10
Purchase #6	$29.54	13.718%	$33.5923	$33.59	$33.60	$33.60
Purchase #7	$228.37	6.357%	$242.8875	$242.89	$242.90	$242.90
7 purchase totals =	$912.24		$969.7507	$969.75	$969.80	$969.80