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	$176.66	9.198%	$192.9092	$192.91	$192.90	$192.90
Purchase #2	$163.69	5.280%	$172.3328	$172.33	$172.35	$172.30
Purchase #3	$123.86	3.785%	$128.5481	$128.55	$128.55	$128.50
Purchase #4	$53.48	8.371%	$57.9568	$57.96	$57.95	$58.00
Purchase #5	$26.36	4.434%	$27.5288	$27.53	$27.55	$27.50
Purchase #6	$29.38	9.408%	$32.1441	$32.14	$32.15	$32.10
Purchase #7	$41.50	5.348%	$43.7194	$43.72	$43.70	$43.70
7 purchase totals =	$614.93		$655.1392	$655.14	$655.15	$655.00