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	$70.86	4.484%	$74.0374	$74.04	$74.05	$74.00
Purchase #2	$199.78	10.351%	$220.4592	$220.46	$220.45	$220.50
Purchase #3	$90.92	8.174%	$98.3518	$98.35	$98.35	$98.40
Purchase #4	$156.73	6.644%	$167.1431	$167.14	$167.15	$167.10
Purchase #5	$80.42	11.255%	$89.4713	$89.47	$89.45	$89.50
Purchase #6	$109.27	10.381%	$120.6133	$120.61	$120.60	$120.60
Purchase #7	$90.65	12.424%	$101.9124	$101.91	$101.90	$101.90
7 purchase totals =	$798.63		$871.9885	$871.98	$871.95	$872.00