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	$197.96	9.174%	$216.1209	$216.12	$216.10	$216.10
Purchase #2	$111.26	10.569%	$123.0191	$123.02	$123.00	$123.00
Purchase #3	$99.41	5.544%	$104.9213	$104.92	$104.90	$104.90
Purchase #4	$244.31	10.661%	$270.3559	$270.36	$270.35	$270.40
Purchase #5	$168.49	12.276%	$189.1738	$189.17	$189.15	$189.20
Purchase #6	$101.73	9.827%	$111.727	$111.73	$111.75	$111.70
Purchase #7	$115.57	5.109%	$121.4745	$121.47	$121.45	$121.50
7 purchase totals =	$1,038.73		$1,136.7925	$1,136.79	$1,136.70	$1,136.80