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	$67.48	7.583%	$72.597	$72.60	$72.60	$72.60
Purchase #2	$236.91	6.162%	$251.5084	$251.51	$251.50	$251.50
Purchase #3	$246.70	3.466%	$255.2506	$255.25	$255.25	$255.30
Purchase #4	$149.58	10.112%	$164.7055	$164.71	$164.70	$164.70
Purchase #5	$28.46	9.464%	$31.1535	$31.15	$31.15	$31.20
Purchase #6	$181.61	11.562%	$202.6077	$202.61	$202.60	$202.60
Purchase #7	$81.75	5.347%	$86.1212	$86.12	$86.10	$86.10
7 purchase totals =	$992.49		$1,063.9439	$1,063.95	$1,063.90	$1,064.00