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	$148.57	5.610%	$156.9048	$156.90	$156.90	$156.90
Purchase #2	$172.66	7.689%	$185.9358	$185.94	$185.95	$185.90
Purchase #3	$24.88	7.572%	$26.7639	$26.76	$26.75	$26.80
Purchase #4	$124.39	3.165%	$128.3269	$128.33	$128.35	$128.30
Purchase #5	$33.57	13.589%	$38.1318	$38.13	$38.15	$38.10
Purchase #6	$146.75	13.366%	$166.3646	$166.36	$166.35	$166.40
Purchase #7	$55.66	3.454%	$57.5825	$57.58	$57.60	$57.60
7 purchase totals =	$706.48		$760.0103	$760.00	$760.05	$760.00