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	$100.36	3.742%	$104.1155	$104.12	$104.10	$104.10
Purchase #2	$214.98	10.748%	$238.0861	$238.09	$238.10	$238.10
Purchase #3	$153.45	3.242%	$158.4248	$158.42	$158.40	$158.40
Purchase #4	$116.68	7.704%	$125.669	$125.67	$125.65	$125.70
Purchase #5	$180.63	8.781%	$196.4911	$196.49	$196.50	$196.50
Purchase #6	$181.27	12.834%	$204.5342	$204.53	$204.55	$204.50
Purchase #7	$35.46	5.511%	$37.4142	$37.41	$37.40	$37.40
7 purchase totals =	$982.83		$1,064.7349	$1,064.73	$1,064.70	$1,064.70