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	$229.28	6.753%	$244.7633	$244.76	$244.75	$244.80
Purchase #2	$28.32	8.292%	$30.6683	$30.67	$30.65	$30.70
Purchase #3	$152.59	10.666%	$168.8652	$168.87	$168.85	$168.90
Purchase #4	$32.70	12.716%	$36.8581	$36.86	$36.85	$36.90
Purchase #5	$199.31	5.274%	$209.8216	$209.82	$209.80	$209.80
Purchase #6	$141.25	6.549%	$150.5005	$150.50	$150.50	$150.50
Purchase #7	$169.71	10.106%	$186.8609	$186.86	$186.85	$186.90
7 purchase totals =	$953.16		$1,028.3379	$1,028.34	$1,028.25	$1,028.50