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	$208.70	6.764%	$222.8165	$222.82	$222.80	$222.80
Purchase #2	$240.35	9.836%	$263.9908	$263.99	$264.00	$264.00
Purchase #3	$180.81	8.785%	$196.6942	$196.69	$196.70	$196.70
Purchase #4	$185.97	6.107%	$197.3272	$197.33	$197.35	$197.30
Purchase #5	$72.41	7.834%	$78.0826	$78.08	$78.10	$78.10
Purchase #6	$38.37	6.724%	$40.95	$40.95	$40.95	$41.00
Purchase #7	$159.25	5.582%	$168.1393	$168.14	$168.15	$168.10
7 purchase totals =	$1,085.86		$1,168.0006	$1,168.00	$1,168.05	$1,168.00