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	$82.78	5.525%	$87.3536	$87.35	$87.35	$87.40
Purchase #2	$152.43	10.568%	$168.5388	$168.54	$168.55	$168.50
Purchase #3	$233.67	7.253%	$250.6181	$250.62	$250.60	$250.60
Purchase #4	$209.49	13.231%	$237.2076	$237.21	$237.20	$237.20
Purchase #5	$161.48	4.662%	$169.0082	$169.01	$169.00	$169.00
Purchase #6	$131.84	12.622%	$148.4808	$148.48	$148.50	$148.50
Purchase #7	$30.59	8.244%	$33.1118	$33.11	$33.10	$33.10
7 purchase totals =	$1,002.28		$1,094.3189	$1,094.32	$1,094.30	$1,094.30