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	$31.79	11.601%	$35.478	$35.48	$35.50	$35.50
Purchase #2	$168.72	10.849%	$187.0244	$187.02	$187.00	$187.00
Purchase #3	$6.92	11.814%	$7.7375	$7.74	$7.75	$7.70
Purchase #4	$198.41	6.765%	$211.8324	$211.83	$211.85	$211.80
Purchase #5	$72.50	11.429%	$80.786	$80.79	$80.80	$80.80
Purchase #6	$63.67	12.533%	$71.6498	$71.65	$71.65	$71.60
Purchase #7	$143.79	11.711%	$160.6292	$160.63	$160.65	$160.60
7 purchase totals =	$685.80		$755.1373	$755.14	$755.20	$755.00