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	$121.73	4.588%	$127.315	$127.32	$127.30	$127.30
Purchase #2	$63.47	3.706%	$65.8222	$65.82	$65.80	$65.80
Purchase #3	$221.33	7.363%	$237.6265	$237.63	$237.65	$237.60
Purchase #4	$158.28	7.276%	$169.7965	$169.80	$169.80	$169.80
Purchase #5	$28.64	10.545%	$31.6601	$31.66	$31.65	$31.70
Purchase #6	$54.75	13.481%	$62.1308	$62.13	$62.15	$62.10
Purchase #7	$33.25	13.578%	$37.7647	$37.76	$37.75	$37.80
7 purchase totals =	$681.45		$732.1158	$732.12	$732.10	$732.10