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	$192.60	4.237%	$200.7605	$200.76	$200.75	$200.80
Purchase #2	$148.37	3.169%	$153.0718	$153.07	$153.05	$153.10
Purchase #3	$106.53	6.778%	$113.7506	$113.75	$113.75	$113.80
Purchase #4	$142.26	12.292%	$159.7466	$159.75	$159.75	$159.70
Purchase #5	$75.50	3.484%	$78.1304	$78.13	$78.15	$78.10
Purchase #6	$25.56	10.566%	$28.2607	$28.26	$28.25	$28.30
Purchase #7	$71.41	10.422%	$78.8524	$78.85	$78.85	$78.90
7 purchase totals =	$762.23		$812.5730	$812.57	$812.55	$812.70