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	$144.69	12.169%	$162.2973	$162.30	$162.30	$162.30
Purchase #2	$205.89	10.435%	$227.3746	$227.37	$227.35	$227.40
Purchase #3	$116.71	3.313%	$120.5766	$120.58	$120.60	$120.60
Purchase #4	$45.89	3.479%	$47.4865	$47.49	$47.50	$47.50
Purchase #5	$152.49	11.385%	$169.851	$169.85	$169.85	$169.90
Purchase #6	$221.76	3.741%	$230.056	$230.06	$230.05	$230.10
Purchase #7	$43.45	5.539%	$45.8567	$45.86	$45.85	$45.90
7 purchase totals =	$930.88		$1,003.4987	$1,003.51	$1,003.50	$1,003.70