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	$181.96	12.799%	$205.2491	$205.25	$205.25	$205.20
Purchase #2	$106.65	3.136%	$109.9945	$109.99	$110.00	$110.00
Purchase #3	$238.78	7.164%	$255.8862	$255.89	$255.90	$255.90
Purchase #4	$134.80	5.187%	$141.7921	$141.79	$141.80	$141.80
Purchase #5	$70.68	8.177%	$76.4595	$76.46	$76.45	$76.50
Purchase #6	$174.81	9.756%	$191.8645	$191.86	$191.85	$191.90
Purchase #7	$91.32	9.672%	$100.1525	$100.15	$100.15	$100.20
7 purchase totals =	$999.00		$1,081.3984	$1,081.39	$1,081.40	$1,081.50