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	$224.31	6.285%	$238.4079	$238.41	$238.40	$238.40
Purchase #2	$144.26	4.227%	$150.3579	$150.36	$150.35	$150.40
Purchase #3	$111.68	8.263%	$120.9081	$120.91	$120.90	$120.90
Purchase #4	$230.75	3.125%	$237.9609	$237.96	$237.95	$238.00
Purchase #5	$56.73	5.548%	$59.8774	$59.88	$59.90	$59.90
Purchase #6	$74.29	5.210%	$78.1605	$78.16	$78.15	$78.20
Purchase #7	$37.75	9.519%	$41.3434	$41.34	$41.35	$41.30
7 purchase totals =	$879.77		$927.0161	$927.02	$927.00	$927.10