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	$139.39	4.774%	$146.0445	$146.04	$146.05	$146.00
Purchase #2	$136.80	7.423%	$146.9547	$146.95	$146.95	$147.00
Purchase #3	$92.83	7.207%	$99.5203	$99.52	$99.50	$99.50
Purchase #4	$5.33	9.663%	$5.845	$5.85	$5.85	$5.80
Purchase #5	$88.33	13.152%	$99.9472	$99.95	$99.95	$99.90
Purchase #6	$88.42	8.829%	$96.2266	$96.23	$96.25	$96.20
Purchase #7	$186.71	10.769%	$206.8168	$206.82	$206.80	$206.80
7 purchase totals =	$737.81		$801.3551	$801.36	$801.35	$801.20