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	$135.85	5.256%	$142.9903	$142.99	$143.00	$143.00
Purchase #2	$151.59	9.111%	$165.4014	$165.40	$165.40	$165.40
Purchase #3	$124.65	3.172%	$128.6039	$128.60	$128.60	$128.60
Purchase #4	$175.61	3.403%	$181.586	$181.59	$181.60	$181.60
Purchase #5	$89.33	6.783%	$95.3893	$95.39	$95.40	$95.40
Purchase #6	$218.74	12.414%	$245.8944	$245.89	$245.90	$245.90
Purchase #7	$8.76	12.179%	$9.8269	$9.83	$9.85	$9.80
7 purchase totals =	$904.53		$969.6922	$969.69	$969.75	$969.70