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	$78.94	13.795%	$89.8298	$89.83	$89.85	$89.80
Purchase #2	$125.93	9.872%	$138.3618	$138.36	$138.35	$138.40
Purchase #3	$248.55	8.507%	$269.6941	$269.69	$269.70	$269.70
Purchase #4	$10.69	5.765%	$11.3063	$11.31	$11.30	$11.30
Purchase #5	$180.30	4.835%	$189.0175	$189.02	$189.00	$189.00
Purchase #6	$165.27	6.794%	$176.4984	$176.50	$176.50	$176.50
Purchase #7	$125.76	12.727%	$141.7655	$141.77	$141.75	$141.80
7 purchase totals =	$935.44		$1,016.4734	$1,016.48	$1,016.45	$1,016.50