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	$51.91	6.583%	$55.3272	$55.33	$55.35	$55.30
Purchase #2	$118.59	7.347%	$127.3028	$127.30	$127.30	$127.30
Purchase #3	$164.42	6.378%	$174.9067	$174.91	$174.90	$174.90
Purchase #4	$156.95	12.603%	$176.7304	$176.73	$176.75	$176.70
Purchase #5	$85.83	11.363%	$95.5829	$95.58	$95.60	$95.60
Purchase #6	$150.40	12.757%	$169.5865	$169.59	$169.60	$169.60
Purchase #7	$227.53	12.431%	$255.8143	$255.81	$255.80	$255.80
7 purchase totals =	$955.63		$1,055.2508	$1,055.25	$1,055.30	$1,055.20