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	$153.90	7.433%	$165.3394	$165.34	$165.35	$165.30
Purchase #2	$74.34	10.839%	$82.3977	$82.40	$82.40	$82.40
Purchase #3	$233.89	13.720%	$265.9797	$265.98	$266.00	$266.00
Purchase #4	$157.77	9.365%	$172.5452	$172.55	$172.55	$172.50
Purchase #5	$229.64	4.600%	$240.2034	$240.20	$240.20	$240.20
Purchase #6	$55.31	8.298%	$59.8996	$59.90	$59.90	$59.90
Purchase #7	$155.48	8.747%	$169.0798	$169.08	$169.10	$169.10
7 purchase totals =	$1,060.33		$1,155.4448	$1,155.45	$1,155.50	$1,155.40