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	$14.31	3.342%	$14.7882	$14.79	$14.80	$14.80
Purchase #2	$63.77	11.780%	$71.2821	$71.28	$71.30	$71.30
Purchase #3	$17.54	4.553%	$18.3386	$18.34	$18.35	$18.30
Purchase #4	$65.81	13.437%	$74.6529	$74.65	$74.65	$74.70
Purchase #5	$161.72	4.157%	$168.4427	$168.44	$168.45	$168.40
Purchase #6	$158.67	8.237%	$171.7396	$171.74	$171.75	$171.70
Purchase #7	$72.49	13.141%	$82.0159	$82.02	$82.00	$82.00
7 purchase totals =	$554.31		$601.2600	$601.26	$601.30	$601.20