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	$86.51	11.259%	$96.2502	$96.25	$96.25	$96.30
Purchase #2	$112.88	12.812%	$127.3422	$127.34	$127.35	$127.30
Purchase #3	$154.31	11.826%	$172.5587	$172.56	$172.55	$172.60
Purchase #4	$156.27	10.139%	$172.1142	$172.11	$172.10	$172.10
Purchase #5	$200.75	8.377%	$217.5668	$217.57	$217.55	$217.60
Purchase #6	$49.96	13.314%	$56.6117	$56.61	$56.60	$56.60
Purchase #7	$147.36	6.705%	$157.2405	$157.24	$157.25	$157.20
7 purchase totals =	$908.04		$999.6843	$999.68	$999.65	$999.70