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	$112.79	9.322%	$123.3043	$123.30	$123.30	$123.30
Purchase #2	$82.87	7.802%	$89.3355	$89.34	$89.35	$89.30
Purchase #3	$239.93	6.163%	$254.7169	$254.72	$254.70	$254.70
Purchase #4	$205.64	6.415%	$218.8318	$218.83	$218.85	$218.80
Purchase #5	$116.65	9.766%	$128.042	$128.04	$128.05	$128.00
Purchase #6	$9.41	9.646%	$10.3177	$10.32	$10.30	$10.30
Purchase #7	$191.67	9.863%	$210.5744	$210.57	$210.55	$210.60
7 purchase totals =	$958.96		$1,035.1226	$1,035.12	$1,035.10	$1,035.00