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	$199.33	3.329%	$205.9657	$205.97	$205.95	$206.00
Purchase #2	$29.80	5.424%	$31.4164	$31.42	$31.40	$31.40
Purchase #3	$35.48	5.245%	$37.3409	$37.34	$37.35	$37.30
Purchase #4	$160.45	8.642%	$174.3161	$174.32	$174.30	$174.30
Purchase #5	$40.95	10.571%	$45.2788	$45.28	$45.30	$45.30
Purchase #6	$105.41	5.460%	$111.1654	$111.17	$111.15	$111.20
Purchase #7	$26.63	7.715%	$28.6845	$28.68	$28.70	$28.70
7 purchase totals =	$598.05		$634.1678	$634.18	$634.15	$634.20