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	$156.58	6.431%	$166.6497	$166.65	$166.65	$166.60
Purchase #2	$221.72	12.550%	$249.5459	$249.55	$249.55	$249.50
Purchase #3	$203.25	12.188%	$228.0221	$228.02	$228.00	$228.00
Purchase #4	$103.43	7.874%	$111.5741	$111.57	$111.55	$111.60
Purchase #5	$49.34	3.729%	$51.1799	$51.18	$51.20	$51.20
Purchase #6	$87.60	12.252%	$98.3328	$98.33	$98.35	$98.30
Purchase #7	$148.29	6.792%	$158.3619	$158.36	$158.35	$158.40
7 purchase totals =	$970.21		$1,063.6664	$1,063.66	$1,063.65	$1,063.60