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	$29.84	8.290%	$32.3137	$32.31	$32.30	$32.30
Purchase #2	$125.77	4.846%	$131.8648	$131.86	$131.85	$131.90
Purchase #3	$99.76	11.306%	$111.0389	$111.04	$111.05	$111.00
Purchase #4	$45.99	3.336%	$47.5242	$47.52	$47.50	$47.50
Purchase #5	$160.62	12.397%	$180.5321	$180.53	$180.55	$180.50
Purchase #6	$32.47	8.803%	$35.3283	$35.33	$35.35	$35.30
Purchase #7	$180.44	3.347%	$186.4793	$186.48	$186.50	$186.50
7 purchase totals =	$674.89		$725.0813	$725.07	$725.10	$725.00