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	$64.95	11.667%	$72.5277	$72.53	$72.55	$72.50
Purchase #2	$119.58	7.404%	$128.4337	$128.43	$128.45	$128.40
Purchase #3	$52.30	10.360%	$57.7183	$57.72	$57.70	$57.70
Purchase #4	$179.52	5.614%	$189.5983	$189.60	$189.60	$189.60
Purchase #5	$30.50	10.387%	$33.668	$33.67	$33.65	$33.70
Purchase #6	$85.75	6.257%	$91.1154	$91.12	$91.10	$91.10
Purchase #7	$223.27	8.730%	$242.7615	$242.76	$242.75	$242.80
7 purchase totals =	$755.87		$815.8229	$815.83	$815.80	$815.80