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	$132.46	7.592%	$142.5164	$142.52	$142.50	$142.50
Purchase #2	$211.73	3.731%	$219.6296	$219.63	$219.65	$219.60
Purchase #3	$12.87	8.461%	$13.9589	$13.96	$13.95	$14.00
Purchase #4	$220.27	13.171%	$249.2818	$249.28	$249.30	$249.30
Purchase #5	$62.82	12.766%	$70.8396	$70.84	$70.85	$70.80
Purchase #6	$73.54	7.285%	$78.8974	$78.90	$78.90	$78.90
Purchase #7	$209.44	10.662%	$231.7705	$231.77	$231.75	$231.80
7 purchase totals =	$923.13		$1,006.8942	$1,006.90	$1,006.90	$1,006.90