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	$86.93	5.865%	$92.0284	$92.03	$92.05	$92.00
Purchase #2	$65.30	9.607%	$71.5734	$71.57	$71.55	$71.60
Purchase #3	$202.80	5.502%	$213.9581	$213.96	$213.95	$214.00
Purchase #4	$235.73	8.244%	$255.1636	$255.16	$255.15	$255.20
Purchase #5	$40.66	6.666%	$43.3704	$43.37	$43.35	$43.40
Purchase #6	$85.25	5.845%	$90.2329	$90.23	$90.25	$90.20
Purchase #7	$104.28	11.552%	$116.3264	$116.33	$116.35	$116.30
7 purchase totals =	$820.95		$882.6532	$882.65	$882.65	$882.70