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	$139.71	9.165%	$152.5144	$152.51	$152.50	$152.50
Purchase #2	$31.86	5.359%	$33.5674	$33.57	$33.55	$33.60
Purchase #3	$128.33	11.531%	$143.1277	$143.13	$143.15	$143.10
Purchase #4	$156.92	6.636%	$167.3332	$167.33	$167.35	$167.30
Purchase #5	$149.37	12.227%	$167.6335	$167.63	$167.65	$167.60
Purchase #6	$224.96	9.417%	$246.1445	$246.14	$246.15	$246.10
Purchase #7	$146.28	4.764%	$153.2488	$153.25	$153.25	$153.20
7 purchase totals =	$977.43		$1,063.5695	$1,063.56	$1,063.60	$1,063.40