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	$144.39	4.227%	$150.4934	$150.49	$150.50	$150.50
Purchase #2	$82.25	9.774%	$90.2891	$90.29	$90.30	$90.30
Purchase #3	$98.77	7.418%	$106.0968	$106.10	$106.10	$106.10
Purchase #4	$158.34	8.760%	$172.2106	$172.21	$172.20	$172.20
Purchase #5	$40.38	10.282%	$44.5319	$44.53	$44.55	$44.50
Purchase #6	$223.80	3.412%	$231.4361	$231.44	$231.45	$231.40
Purchase #7	$219.51	8.504%	$238.1771	$238.18	$238.20	$238.20
7 purchase totals =	$967.44		$1,033.2350	$1,033.24	$1,033.30	$1,033.20