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	$174.37	5.221%	$183.4739	$183.47	$183.45	$183.50
Purchase #2	$236.29	8.754%	$256.9748	$256.97	$256.95	$257.00
Purchase #3	$48.84	7.551%	$52.5279	$52.53	$52.55	$52.50
Purchase #4	$31.50	12.686%	$35.4961	$35.50	$35.50	$35.50
Purchase #5	$104.69	3.178%	$108.017	$108.02	$108.00	$108.00
Purchase #6	$79.35	12.765%	$89.479	$89.48	$89.50	$89.50
Purchase #7	$41.84	8.367%	$45.3408	$45.34	$45.35	$45.30
7 purchase totals =	$716.88		$771.3095	$771.31	$771.30	$771.30