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	$202.56	4.114%	$210.8933	$210.89	$210.90	$210.90
Purchase #2	$75.43	5.201%	$79.3531	$79.35	$79.35	$79.40
Purchase #3	$17.75	11.215%	$19.7407	$19.74	$19.75	$19.70
Purchase #4	$29.56	6.560%	$31.4991	$31.50	$31.50	$31.50
Purchase #5	$85.93	6.659%	$91.6521	$91.65	$91.65	$91.70
Purchase #6	$37.50	5.189%	$39.4459	$39.45	$39.45	$39.40
Purchase #7	$69.71	12.343%	$78.3143	$78.31	$78.30	$78.30
7 purchase totals =	$518.44		$550.8985	$550.89	$550.90	$550.90