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	$207.39	3.672%	$215.0054	$215.01	$215.00	$215.00
Purchase #2	$124.97	5.842%	$132.2707	$132.27	$132.25	$132.30
Purchase #3	$29.96	6.174%	$31.8097	$31.81	$31.80	$31.80
Purchase #4	$148.83	11.779%	$166.3607	$166.36	$166.35	$166.40
Purchase #5	$160.49	4.106%	$167.0797	$167.08	$167.10	$167.10
Purchase #6	$18.25	12.134%	$20.4645	$20.46	$20.45	$20.50
Purchase #7	$89.34	3.147%	$92.1515	$92.15	$92.15	$92.20
7 purchase totals =	$779.23		$825.1422	$825.14	$825.10	$825.30