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	$86.92	3.493%	$89.9561	$89.96	$89.95	$90.00
Purchase #2	$56.84	5.736%	$60.1003	$60.10	$60.10	$60.10
Purchase #3	$42.59	7.264%	$45.6837	$45.68	$45.70	$45.70
Purchase #4	$140.25	4.709%	$146.8544	$146.85	$146.85	$146.90
Purchase #5	$233.87	11.853%	$261.5906	$261.59	$261.60	$261.60
Purchase #6	$96.86	8.413%	$105.0088	$105.01	$105.00	$105.00
Purchase #7	$39.85	7.250%	$42.7391	$42.74	$42.75	$42.70
7 purchase totals =	$697.18		$751.9330	$751.93	$751.95	$752.00