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	$194.76	5.342%	$205.1641	$205.16	$205.15	$205.20
Purchase #2	$49.64	9.244%	$54.2287	$54.23	$54.25	$54.20
Purchase #3	$80.69	12.287%	$90.6044	$90.60	$90.60	$90.60
Purchase #4	$156.53	11.755%	$174.9301	$174.93	$174.95	$174.90
Purchase #5	$241.56	13.837%	$274.9847	$274.98	$275.00	$275.00
Purchase #6	$208.79	9.382%	$228.3787	$228.38	$228.40	$228.40
Purchase #7	$70.67	5.580%	$74.6134	$74.61	$74.60	$74.60
7 purchase totals =	$1,002.64		$1,102.9041	$1,102.89	$1,102.95	$1,102.90