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	$215.66	6.472%	$229.6175	$229.62	$229.60	$229.60
Purchase #2	$48.67	11.143%	$54.0933	$54.09	$54.10	$54.10
Purchase #3	$36.92	5.316%	$38.8827	$38.88	$38.90	$38.90
Purchase #4	$129.63	3.166%	$133.7341	$133.73	$133.75	$133.70
Purchase #5	$196.42	4.512%	$205.2825	$205.28	$205.30	$205.30
Purchase #6	$82.46	9.171%	$90.0224	$90.02	$90.00	$90.00
Purchase #7	$105.59	3.356%	$109.1336	$109.13	$109.15	$109.10
7 purchase totals =	$815.35		$860.7661	$860.75	$860.80	$860.70