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	$35.51	5.520%	$37.4702	$37.47	$37.45	$37.50
Purchase #2	$225.92	8.856%	$245.9275	$245.93	$245.95	$245.90
Purchase #3	$218.41	10.636%	$241.6401	$241.64	$241.65	$241.60
Purchase #4	$35.97	3.411%	$37.1969	$37.20	$37.20	$37.20
Purchase #5	$215.68	3.575%	$223.3906	$223.39	$223.40	$223.40
Purchase #6	$106.76	7.332%	$114.5876	$114.59	$114.60	$114.60
Purchase #7	$142.75	7.606%	$153.6076	$153.61	$153.60	$153.60
7 purchase totals =	$981.00		$1,053.8205	$1,053.83	$1,053.85	$1,053.80