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	$98.41	5.704%	$104.0233	$104.02	$104.00	$104.00
Purchase #2	$24.80	7.328%	$26.6173	$26.62	$26.60	$26.60
Purchase #3	$230.53	6.345%	$245.1571	$245.16	$245.15	$245.20
Purchase #4	$95.82	7.739%	$103.2355	$103.24	$103.25	$103.20
Purchase #5	$200.33	11.503%	$223.374	$223.37	$223.35	$223.40
Purchase #6	$179.61	10.534%	$198.5301	$198.53	$198.55	$198.50
Purchase #7	$80.26	12.859%	$90.5806	$90.58	$90.60	$90.60
7 purchase totals =	$909.76		$991.5179	$991.52	$991.50	$991.50