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	$92.95	6.530%	$99.0196	$99.02	$99.00	$99.00
Purchase #2	$175.56	12.119%	$196.8361	$196.84	$196.85	$196.80
Purchase #3	$202.71	4.700%	$212.2374	$212.24	$212.25	$212.20
Purchase #4	$141.54	11.802%	$158.2446	$158.24	$158.25	$158.20
Purchase #5	$113.45	9.741%	$124.5012	$124.50	$124.50	$124.50
Purchase #6	$100.41	12.183%	$112.643	$112.64	$112.65	$112.60
Purchase #7	$129.98	12.696%	$146.4823	$146.48	$146.50	$146.50
7 purchase totals =	$956.60		$1,049.9642	$1,049.96	$1,050.00	$1,049.80