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	$216.78	6.759%	$231.4322	$231.43	$231.45	$231.40
Purchase #2	$160.56	13.113%	$181.6142	$181.61	$181.60	$181.60
Purchase #3	$250.35	10.801%	$277.3903	$277.39	$277.40	$277.40
Purchase #4	$71.25	6.634%	$75.9767	$75.98	$76.00	$76.00
Purchase #5	$99.32	3.658%	$102.9531	$102.95	$102.95	$103.00
Purchase #6	$81.99	11.561%	$91.4689	$91.47	$91.45	$91.50
Purchase #7	$44.93	3.295%	$46.4104	$46.41	$46.40	$46.40
7 purchase totals =	$925.18		$1,007.2458	$1,007.24	$1,007.25	$1,007.30