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	$217.26	12.838%	$245.1518	$245.15	$245.15	$245.20
Purchase #2	$124.90	12.425%	$140.4188	$140.42	$140.40	$140.40
Purchase #3	$164.72	4.400%	$171.9677	$171.97	$171.95	$172.00
Purchase #4	$138.81	11.696%	$155.0452	$155.05	$155.05	$155.00
Purchase #5	$228.36	11.587%	$254.8201	$254.82	$254.80	$254.80
Purchase #6	$35.94	4.376%	$37.5127	$37.51	$37.50	$37.50
Purchase #7	$92.74	13.595%	$105.348	$105.35	$105.35	$105.30
7 purchase totals =	$1,002.73		$1,110.2643	$1,110.27	$1,110.20	$1,110.20