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	$91.30	5.872%	$96.6611	$96.66	$96.65	$96.70
Purchase #2	$227.27	13.197%	$257.2628	$257.26	$257.25	$257.30
Purchase #3	$75.40	6.712%	$80.4608	$80.46	$80.45	$80.50
Purchase #4	$196.56	5.188%	$206.7575	$206.76	$206.75	$206.80
Purchase #5	$231.57	3.643%	$240.0061	$240.01	$240.00	$240.00
Purchase #6	$31.78	5.236%	$33.444	$33.44	$33.45	$33.40
Purchase #7	$161.30	12.142%	$180.885	$180.89	$180.90	$180.90
7 purchase totals =	$1,015.18		$1,095.4773	$1,095.48	$1,095.45	$1,095.60