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	$82.70	3.176%	$85.3266	$85.33	$85.35	$85.30
Purchase #2	$25.74	12.502%	$28.958	$28.96	$28.95	$29.00
Purchase #3	$81.92	12.398%	$92.0764	$92.08	$92.10	$92.10
Purchase #4	$73.77	12.130%	$82.7183	$82.72	$82.70	$82.70
Purchase #5	$7.35	5.335%	$7.7421	$7.74	$7.75	$7.70
Purchase #6	$192.96	10.655%	$213.5199	$213.52	$213.50	$213.50
Purchase #7	$64.57	12.114%	$72.392	$72.39	$72.40	$72.40
7 purchase totals =	$529.01		$582.7333	$582.74	$582.75	$582.70