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	$218.68	5.814%	$231.3941	$231.39	$231.40	$231.40
Purchase #2	$53.62	10.701%	$59.3579	$59.36	$59.35	$59.40
Purchase #3	$33.42	6.734%	$35.6705	$35.67	$35.65	$35.70
Purchase #4	$65.80	13.762%	$74.8554	$74.86	$74.85	$74.90
Purchase #5	$27.88	3.533%	$28.865	$28.87	$28.85	$28.90
Purchase #6	$204.52	7.335%	$219.5215	$219.52	$219.50	$219.50
Purchase #7	$73.30	13.481%	$83.1816	$83.18	$83.20	$83.20
7 purchase totals =	$677.22		$732.8460	$732.85	$732.80	$733.00