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	$149.40	9.567%	$163.6931	$163.69	$163.70	$163.70
Purchase #2	$140.56	10.667%	$155.5535	$155.55	$155.55	$155.60
Purchase #3	$72.78	13.376%	$82.5151	$82.52	$82.50	$82.50
Purchase #4	$196.69	10.279%	$216.9078	$216.91	$216.90	$216.90
Purchase #5	$171.93	5.567%	$181.5013	$181.50	$181.50	$181.50
Purchase #6	$33.25	10.849%	$36.8573	$36.86	$36.85	$36.90
Purchase #7	$215.47	12.363%	$242.1086	$242.11	$242.10	$242.10
7 purchase totals =	$980.08		$1,079.1367	$1,079.14	$1,079.10	$1,079.20