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	$172.87	13.573%	$196.3336	$196.33	$196.35	$196.30
Purchase #2	$32.64	13.687%	$37.1074	$37.11	$37.10	$37.10
Purchase #3	$239.97	4.609%	$251.0302	$251.03	$251.05	$251.00
Purchase #4	$20.67	12.437%	$23.2407	$23.24	$23.25	$23.20
Purchase #5	$126.83	11.516%	$141.4357	$141.44	$141.45	$141.40
Purchase #6	$112.61	13.682%	$128.0173	$128.02	$128.00	$128.00
Purchase #7	$214.98	12.190%	$241.1861	$241.19	$241.20	$241.20
7 purchase totals =	$920.57		$1,018.3510	$1,018.36	$1,018.40	$1,018.20