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	$197.51	4.404%	$206.2083	$206.21	$206.20	$206.20
Purchase #2	$92.56	5.536%	$97.6841	$97.68	$97.70	$97.70
Purchase #3	$34.59	8.676%	$37.591	$37.59	$37.60	$37.60
Purchase #4	$166.73	12.687%	$187.883	$187.88	$187.90	$187.90
Purchase #5	$121.66	13.851%	$138.5111	$138.51	$138.50	$138.50
Purchase #6	$187.37	12.589%	$210.958	$210.96	$210.95	$211.00
Purchase #7	$123.89	12.383%	$139.2313	$139.23	$139.25	$139.20
7 purchase totals =	$924.31		$1,018.0668	$1,018.06	$1,018.10	$1,018.10