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	$88.84	7.532%	$95.5314	$95.53	$95.55	$95.50
Purchase #2	$168.82	6.188%	$179.2666	$179.27	$179.25	$179.30
Purchase #3	$69.59	7.478%	$74.7939	$74.79	$74.80	$74.80
Purchase #4	$18.43	11.514%	$20.552	$20.55	$20.55	$20.60
Purchase #5	$72.52	8.434%	$78.6363	$78.64	$78.65	$78.60
Purchase #6	$170.25	4.838%	$178.4867	$178.49	$178.50	$178.50
Purchase #7	$22.53	4.550%	$23.5551	$23.56	$23.55	$23.60
7 purchase totals =	$610.98		$650.8220	$650.83	$650.85	$650.90