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	$34.61	3.549%	$35.8383	$35.84	$35.85	$35.80
Purchase #2	$90.84	13.240%	$102.8672	$102.87	$102.85	$102.90
Purchase #3	$180.80	10.828%	$200.377	$200.38	$200.40	$200.40
Purchase #4	$187.69	6.507%	$199.903	$199.90	$199.90	$199.90
Purchase #5	$183.63	7.731%	$197.8264	$197.83	$197.85	$197.80
Purchase #6	$118.83	10.366%	$131.1479	$131.15	$131.15	$131.10
Purchase #7	$134.85	6.331%	$143.3874	$143.39	$143.40	$143.40
7 purchase totals =	$931.25		$1,011.3472	$1,011.36	$1,011.40	$1,011.30