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	$167.54	12.121%	$187.8475	$187.85	$187.85	$187.80
Purchase #2	$202.45	7.122%	$216.8685	$216.87	$216.85	$216.90
Purchase #3	$38.39	10.435%	$42.396	$42.40	$42.40	$42.40
Purchase #4	$231.83	10.731%	$256.7077	$256.71	$256.70	$256.70
Purchase #5	$206.38	12.390%	$231.9505	$231.95	$231.95	$232.00
Purchase #6	$114.38	4.261%	$119.2537	$119.25	$119.25	$119.30
Purchase #7	$246.86	7.113%	$264.4192	$264.42	$264.40	$264.40
7 purchase totals =	$1,207.83		$1,319.4431	$1,319.45	$1,319.40	$1,319.50