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	$52.27	10.310%	$57.659	$57.66	$57.65	$57.70
Purchase #2	$57.86	8.206%	$62.608	$62.61	$62.60	$62.60
Purchase #3	$89.56	13.763%	$101.8861	$101.89	$101.90	$101.90
Purchase #4	$233.80	4.284%	$243.816	$243.82	$243.80	$243.80
Purchase #5	$109.65	6.845%	$117.1555	$117.16	$117.15	$117.20
Purchase #6	$35.34	9.707%	$38.7705	$38.77	$38.75	$38.80
Purchase #7	$63.41	6.185%	$67.3319	$67.33	$67.35	$67.30
7 purchase totals =	$641.89		$689.2270	$689.24	$689.20	$689.30