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	$131.94	13.343%	$149.5448	$149.54	$149.55	$149.50
Purchase #2	$35.56	6.757%	$37.9628	$37.96	$37.95	$38.00
Purchase #3	$159.72	5.582%	$168.6356	$168.64	$168.65	$168.60
Purchase #4	$233.44	9.417%	$255.423	$255.42	$255.40	$255.40
Purchase #5	$90.66	13.867%	$103.2318	$103.23	$103.25	$103.20
Purchase #6	$68.34	8.445%	$74.1113	$74.11	$74.10	$74.10
Purchase #7	$108.99	12.858%	$123.0039	$123.00	$123.00	$123.00
7 purchase totals =	$828.65		$911.9132	$911.90	$911.90	$911.80