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	$88.92	4.417%	$92.8476	$92.85	$92.85	$92.80
Purchase #2	$111.71	12.595%	$125.7799	$125.78	$125.80	$125.80
Purchase #3	$64.31	4.371%	$67.121	$67.12	$67.10	$67.10
Purchase #4	$59.98	4.328%	$62.5759	$62.58	$62.60	$62.60
Purchase #5	$56.73	4.281%	$59.1586	$59.16	$59.15	$59.20
Purchase #6	$93.41	8.475%	$101.3265	$101.33	$101.35	$101.30
Purchase #7	$29.63	6.688%	$31.6117	$31.61	$31.60	$31.60
7 purchase totals =	$504.69		$540.4212	$540.43	$540.45	$540.40