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	$150.94	11.320%	$168.0264	$168.03	$168.05	$168.00
Purchase #2	$101.99	11.655%	$113.8769	$113.88	$113.90	$113.90
Purchase #3	$233.67	6.818%	$249.6016	$249.60	$249.60	$249.60
Purchase #4	$18.90	3.211%	$19.5069	$19.51	$19.50	$19.50
Purchase #5	$63.85	12.862%	$72.0624	$72.06	$72.05	$72.10
Purchase #6	$205.32	3.240%	$211.9724	$211.97	$211.95	$212.00
Purchase #7	$197.87	9.594%	$216.8536	$216.85	$216.85	$216.90
7 purchase totals =	$972.54		$1,051.9002	$1,051.90	$1,051.90	$1,052.00