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	$156.97	9.504%	$171.8884	$171.89	$171.90	$171.90
Purchase #2	$172.71	3.514%	$178.779	$178.78	$178.80	$178.80
Purchase #3	$84.84	3.400%	$87.7246	$87.72	$87.70	$87.70
Purchase #4	$185.50	3.151%	$191.3451	$191.35	$191.35	$191.30
Purchase #5	$137.49	4.402%	$143.5423	$143.54	$143.55	$143.50
Purchase #6	$157.41	3.483%	$162.8926	$162.89	$162.90	$162.90
Purchase #7	$167.60	4.513%	$175.1638	$175.16	$175.15	$175.20
7 purchase totals =	$1,062.52		$1,111.3358	$1,111.33	$1,111.35	$1,111.30