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	$187.61	13.260%	$212.4871	$212.49	$212.50	$212.50
Purchase #2	$92.44	6.478%	$98.4283	$98.43	$98.45	$98.40
Purchase #3	$37.45	8.781%	$40.7385	$40.74	$40.75	$40.70
Purchase #4	$83.32	7.398%	$89.484	$89.48	$89.50	$89.50
Purchase #5	$96.29	13.246%	$109.0446	$109.04	$109.05	$109.00
Purchase #6	$22.51	5.400%	$23.7255	$23.73	$23.75	$23.70
Purchase #7	$146.67	10.351%	$161.8518	$161.85	$161.85	$161.90
7 purchase totals =	$666.29		$735.7598	$735.76	$735.85	$735.70