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	$202.69	10.356%	$223.6806	$223.68	$223.70	$223.70
Purchase #2	$105.80	8.435%	$114.7242	$114.72	$114.70	$114.70
Purchase #3	$185.39	8.336%	$200.8441	$200.84	$200.85	$200.80
Purchase #4	$97.85	3.147%	$100.9293	$100.93	$100.95	$100.90
Purchase #5	$211.52	6.600%	$225.4803	$225.48	$225.50	$225.50
Purchase #6	$82.59	12.764%	$93.1318	$93.13	$93.15	$93.10
Purchase #7	$77.62	5.531%	$81.9132	$81.91	$81.90	$81.90
7 purchase totals =	$963.46		$1,040.7035	$1,040.69	$1,040.75	$1,040.60