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	$210.65	13.106%	$238.2578	$238.26	$238.25	$238.30
Purchase #2	$83.53	9.170%	$91.1897	$91.19	$91.20	$91.20
Purchase #3	$228.87	9.151%	$249.8139	$249.81	$249.80	$249.80
Purchase #4	$81.76	12.181%	$91.7192	$91.72	$91.70	$91.70
Purchase #5	$90.78	9.776%	$99.6547	$99.65	$99.65	$99.70
Purchase #6	$131.96	9.148%	$144.0317	$144.03	$144.05	$144.00
Purchase #7	$189.74	3.370%	$196.1342	$196.13	$196.15	$196.10
7 purchase totals =	$1,017.29		$1,110.8012	$1,110.79	$1,110.80	$1,110.80