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	$244.26	11.166%	$271.5341	$271.53	$271.55	$271.50
Purchase #2	$214.35	6.600%	$228.4971	$228.50	$228.50	$228.50
Purchase #3	$155.37	3.413%	$160.6728	$160.67	$160.65	$160.70
Purchase #4	$196.52	7.821%	$211.8898	$211.89	$211.90	$211.90
Purchase #5	$146.80	13.483%	$166.593	$166.59	$166.60	$166.60
Purchase #6	$100.32	12.289%	$112.6483	$112.65	$112.65	$112.60
Purchase #7	$189.69	10.400%	$209.4178	$209.42	$209.40	$209.40
7 purchase totals =	$1,247.31		$1,361.2529	$1,361.25	$1,361.25	$1,361.20