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	$241.26	10.476%	$266.5344	$266.53	$266.55	$266.50
Purchase #2	$91.98	12.260%	$103.2567	$103.26	$103.25	$103.30
Purchase #3	$32.42	12.261%	$36.395	$36.40	$36.40	$36.40
Purchase #4	$33.56	6.750%	$35.8253	$35.83	$35.85	$35.80
Purchase #5	$149.45	12.770%	$168.5348	$168.53	$168.55	$168.50
Purchase #6	$48.44	11.461%	$53.9917	$53.99	$54.00	$54.00
Purchase #7	$33.39	13.192%	$37.7948	$37.79	$37.80	$37.80
7 purchase totals =	$630.50		$702.3327	$702.33	$702.40	$702.30