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	$187.38	9.534%	$205.2448	$205.24	$205.25	$205.20
Purchase #2	$141.98	7.211%	$152.2182	$152.22	$152.20	$152.20
Purchase #3	$81.96	9.599%	$89.8273	$89.83	$89.85	$89.80
Purchase #4	$140.47	3.782%	$145.7826	$145.78	$145.80	$145.80
Purchase #5	$118.28	4.437%	$123.5281	$123.53	$123.55	$123.50
Purchase #6	$216.47	5.867%	$229.1703	$229.17	$229.15	$229.20
Purchase #7	$236.42	13.197%	$267.6203	$267.62	$267.60	$267.60
7 purchase totals =	$1,122.96		$1,213.3916	$1,213.39	$1,213.40	$1,213.30