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	$190.34	3.280%	$196.5832	$196.58	$196.60	$196.60
Purchase #2	$197.47	4.620%	$206.5931	$206.59	$206.60	$206.60
Purchase #3	$103.96	8.179%	$112.4629	$112.46	$112.45	$112.50
Purchase #4	$55.43	3.280%	$57.2481	$57.25	$57.25	$57.20
Purchase #5	$221.50	7.369%	$237.8223	$237.82	$237.80	$237.80
Purchase #6	$6.41	11.400%	$7.1407	$7.14	$7.15	$7.10
Purchase #7	$215.39	11.187%	$239.4857	$239.49	$239.50	$239.50
7 purchase totals =	$990.50		$1,057.3360	$1,057.33	$1,057.35	$1,057.30