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	$100.90	8.548%	$109.5249	$109.52	$109.50	$109.50
Purchase #2	$6.52	7.449%	$7.0057	$7.01	$7.00	$7.00
Purchase #3	$102.74	9.828%	$112.8373	$112.84	$112.85	$112.80
Purchase #4	$32.46	7.556%	$34.9127	$34.91	$34.90	$34.90
Purchase #5	$147.91	13.118%	$167.3128	$167.31	$167.30	$167.30
Purchase #6	$82.55	9.502%	$90.3939	$90.39	$90.40	$90.40
Purchase #7	$205.58	3.703%	$213.1926	$213.19	$213.20	$213.20
7 purchase totals =	$678.66		$735.1799	$735.17	$735.15	$735.10