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	$111.75	12.447%	$125.6595	$125.66	$125.65	$125.70
Purchase #2	$97.73	7.414%	$104.9757	$104.98	$105.00	$105.00
Purchase #3	$80.94	12.321%	$90.9126	$90.91	$90.90	$90.90
Purchase #4	$83.85	3.443%	$86.737	$86.74	$86.75	$86.70
Purchase #5	$28.51	11.414%	$31.7641	$31.76	$31.75	$31.80
Purchase #6	$164.57	13.571%	$186.9038	$186.90	$186.90	$186.90
Purchase #7	$146.35	8.612%	$158.9537	$158.95	$158.95	$159.00
7 purchase totals =	$713.70		$785.9064	$785.90	$785.90	$786.00