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	$222.41	3.353%	$229.8674	$229.87	$229.85	$229.90
Purchase #2	$34.56	3.365%	$35.7229	$35.72	$35.70	$35.70
Purchase #3	$209.86	6.661%	$223.8388	$223.84	$223.85	$223.80
Purchase #4	$236.97	4.834%	$248.4251	$248.43	$248.45	$248.40
Purchase #5	$137.92	9.407%	$150.8941	$150.89	$150.90	$150.90
Purchase #6	$242.76	10.648%	$268.6091	$268.61	$268.60	$268.60
Purchase #7	$199.82	13.178%	$226.1523	$226.15	$226.15	$226.20
7 purchase totals =	$1,284.30		$1,383.5097	$1,383.51	$1,383.50	$1,383.50