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	$32.95	6.498%	$35.0911	$35.09	$35.10	$35.10
Purchase #2	$60.48	4.803%	$63.3849	$63.38	$63.40	$63.40
Purchase #3	$84.65	7.557%	$91.047	$91.05	$91.05	$91.00
Purchase #4	$191.59	9.229%	$209.2718	$209.27	$209.25	$209.30
Purchase #5	$168.31	11.257%	$187.2567	$187.26	$187.25	$187.30
Purchase #6	$132.31	9.510%	$144.8927	$144.89	$144.90	$144.90
Purchase #7	$158.95	4.387%	$165.9231	$165.92	$165.90	$165.90
7 purchase totals =	$829.24		$896.8673	$896.86	$896.85	$896.90