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	$82.28	9.479%	$90.0793	$90.08	$90.10	$90.10
Purchase #2	$202.74	7.441%	$217.8259	$217.83	$217.85	$217.80
Purchase #3	$173.45	11.692%	$193.7298	$193.73	$193.75	$193.70
Purchase #4	$123.30	5.414%	$129.9755	$129.98	$130.00	$130.00
Purchase #5	$140.99	9.586%	$154.5053	$154.51	$154.50	$154.50
Purchase #6	$182.79	8.458%	$198.2504	$198.25	$198.25	$198.30
Purchase #7	$104.39	6.844%	$111.5345	$111.53	$111.55	$111.50
7 purchase totals =	$1,009.94		$1,095.9007	$1,095.91	$1,096.00	$1,095.90