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	$92.45	13.729%	$105.1425	$105.14	$105.15	$105.10
Purchase #2	$73.75	13.710%	$83.8611	$83.86	$83.85	$83.90
Purchase #3	$83.79	8.730%	$91.1049	$91.10	$91.10	$91.10
Purchase #4	$143.25	12.808%	$161.5975	$161.60	$161.60	$161.60
Purchase #5	$138.79	10.181%	$152.9202	$152.92	$152.90	$152.90
Purchase #6	$81.90	5.489%	$86.3955	$86.40	$86.40	$86.40
Purchase #7	$75.51	4.301%	$78.7577	$78.76	$78.75	$78.80
7 purchase totals =	$689.44		$759.7794	$759.78	$759.75	$759.80