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	$72.96	12.749%	$82.2617	$82.26	$82.25	$82.30
Purchase #2	$18.64	9.185%	$20.3521	$20.35	$20.35	$20.40
Purchase #3	$176.78	13.193%	$200.1026	$200.10	$200.10	$200.10
Purchase #4	$112.56	9.598%	$123.3635	$123.36	$123.35	$123.40
Purchase #5	$105.65	5.290%	$111.2389	$111.24	$111.25	$111.20
Purchase #6	$35.98	8.270%	$38.9555	$38.96	$38.95	$39.00
Purchase #7	$46.44	6.123%	$49.2835	$49.28	$49.30	$49.30
7 purchase totals =	$569.01		$625.5578	$625.55	$625.55	$625.70