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	$51.90	10.361%	$57.2774	$57.28	$57.30	$57.30
Purchase #2	$219.53	8.302%	$237.7554	$237.76	$237.75	$237.80
Purchase #3	$240.67	5.700%	$254.3882	$254.39	$254.40	$254.40
Purchase #4	$31.93	10.763%	$35.3666	$35.37	$35.35	$35.40
Purchase #5	$200.52	3.543%	$207.6244	$207.62	$207.60	$207.60
Purchase #6	$215.25	3.188%	$222.1122	$222.11	$222.10	$222.10
Purchase #7	$171.27	6.105%	$181.726	$181.73	$181.75	$181.70
7 purchase totals =	$1,131.07		$1,196.2502	$1,196.26	$1,196.25	$1,196.30