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	$160.43	3.113%	$165.4242	$165.42	$165.40	$165.40
Purchase #2	$83.26	9.474%	$91.1481	$91.15	$91.15	$91.10
Purchase #3	$211.79	7.132%	$226.8949	$226.89	$226.90	$226.90
Purchase #4	$154.77	3.435%	$160.0863	$160.09	$160.10	$160.10
Purchase #5	$95.94	9.742%	$105.2865	$105.29	$105.30	$105.30
Purchase #6	$62.87	6.359%	$66.8679	$66.87	$66.85	$66.90
Purchase #7	$189.44	3.871%	$196.7732	$196.77	$196.75	$196.80
7 purchase totals =	$958.50		$1,012.4811	$1,012.48	$1,012.45	$1,012.50