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	$101.67	8.554%	$110.3669	$110.37	$110.35	$110.40
Purchase #2	$39.66	9.840%	$43.5625	$43.56	$43.55	$43.60
Purchase #3	$26.33	13.487%	$29.8811	$29.88	$29.90	$29.90
Purchase #4	$69.75	12.693%	$78.6034	$78.60	$78.60	$78.60
Purchase #5	$157.29	4.566%	$164.4719	$164.47	$164.45	$164.50
Purchase #6	$12.87	9.743%	$14.1239	$14.12	$14.10	$14.10
Purchase #7	$234.70	4.520%	$245.3084	$245.31	$245.30	$245.30
7 purchase totals =	$642.27		$686.3181	$686.31	$686.25	$686.40