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	$176.35	6.571%	$187.938	$187.94	$187.95	$187.90
Purchase #2	$135.50	10.361%	$149.5392	$149.54	$149.55	$149.50
Purchase #3	$243.89	12.576%	$274.5616	$274.56	$274.55	$274.60
Purchase #4	$136.55	13.873%	$155.4936	$155.49	$155.50	$155.50
Purchase #5	$148.27	5.448%	$156.3477	$156.35	$156.35	$156.30
Purchase #6	$171.32	10.221%	$188.8306	$188.83	$188.85	$188.80
Purchase #7	$65.77	10.529%	$72.6949	$72.69	$72.70	$72.70
7 purchase totals =	$1,077.65		$1,185.4056	$1,185.40	$1,185.45	$1,185.30