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	$102.85	8.215%	$111.2991	$111.30	$111.30	$111.30
Purchase #2	$250.77	12.656%	$282.5075	$282.51	$282.50	$282.50
Purchase #3	$71.86	8.850%	$78.2196	$78.22	$78.20	$78.20
Purchase #4	$146.27	5.541%	$154.3748	$154.37	$154.35	$154.40
Purchase #5	$188.46	13.473%	$213.8512	$213.85	$213.85	$213.90
Purchase #6	$136.25	3.775%	$141.3934	$141.39	$141.40	$141.40
Purchase #7	$166.25	3.148%	$171.4836	$171.48	$171.50	$171.50
7 purchase totals =	$1,062.71		$1,153.1292	$1,153.12	$1,153.10	$1,153.20