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	$58.43	5.815%	$61.8277	$61.83	$61.85	$61.80
Purchase #2	$33.71	12.498%	$37.9231	$37.92	$37.90	$37.90
Purchase #3	$241.53	11.378%	$269.0113	$269.01	$269.00	$269.00
Purchase #4	$83.41	6.781%	$89.066	$89.07	$89.05	$89.10
Purchase #5	$38.34	9.850%	$42.1165	$42.12	$42.10	$42.10
Purchase #6	$87.61	7.467%	$94.1518	$94.15	$94.15	$94.20
Purchase #7	$201.78	6.836%	$215.5737	$215.57	$215.55	$215.60
7 purchase totals =	$744.81		$809.6701	$809.67	$809.60	$809.70