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	$213.79	4.746%	$223.9365	$223.94	$223.95	$223.90
Purchase #2	$230.72	4.406%	$240.8855	$240.89	$240.90	$240.90
Purchase #3	$134.94	11.557%	$150.535	$150.54	$150.55	$150.50
Purchase #4	$12.68	13.770%	$14.426	$14.43	$14.45	$14.40
Purchase #5	$55.61	13.697%	$63.2269	$63.23	$63.25	$63.20
Purchase #6	$232.32	7.708%	$250.2272	$250.23	$250.25	$250.20
Purchase #7	$222.98	4.281%	$232.5258	$232.53	$232.55	$232.50
7 purchase totals =	$1,103.04		$1,175.7629	$1,175.79	$1,175.90	$1,175.60