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	$43.34	6.498%	$46.1562	$46.16	$46.15	$46.20
Purchase #2	$31.28	13.614%	$35.5385	$35.54	$35.55	$35.50
Purchase #3	$225.35	12.364%	$253.2123	$253.21	$253.20	$253.20
Purchase #4	$61.83	5.766%	$65.3951	$65.40	$65.40	$65.40
Purchase #5	$46.28	12.455%	$52.0442	$52.04	$52.05	$52.00
Purchase #6	$210.29	11.665%	$234.8203	$234.82	$234.80	$234.80
Purchase #7	$187.74	6.601%	$200.1327	$200.13	$200.15	$200.10
7 purchase totals =	$806.11		$887.2993	$887.30	$887.30	$887.20