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	$90.74	3.742%	$94.1355	$94.14	$94.15	$94.10
Purchase #2	$133.48	7.194%	$143.0826	$143.08	$143.10	$143.10
Purchase #3	$59.45	10.131%	$65.4729	$65.47	$65.45	$65.50
Purchase #4	$43.71	4.407%	$45.6363	$45.64	$45.65	$45.60
Purchase #5	$181.73	13.655%	$206.5452	$206.55	$206.55	$206.50
Purchase #6	$127.91	12.656%	$144.0983	$144.10	$144.10	$144.10
Purchase #7	$93.46	9.381%	$102.2275	$102.23	$102.25	$102.20
7 purchase totals =	$730.48		$801.1983	$801.21	$801.25	$801.10