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	$110.59	3.440%	$114.3943	$114.39	$114.40	$114.40
Purchase #2	$115.98	10.808%	$128.5151	$128.52	$128.50	$128.50
Purchase #3	$160.91	5.339%	$169.501	$169.50	$169.50	$169.50
Purchase #4	$141.58	8.660%	$153.8408	$153.84	$153.85	$153.80
Purchase #5	$156.75	10.686%	$173.5003	$173.50	$173.50	$173.50
Purchase #6	$185.46	13.544%	$210.5787	$210.58	$210.60	$210.60
Purchase #7	$52.46	12.123%	$58.8197	$58.82	$58.80	$58.80
7 purchase totals =	$923.73		$1,009.1499	$1,009.15	$1,009.15	$1,009.10