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	$188.57	4.380%	$196.8294	$196.83	$196.85	$196.80
Purchase #2	$168.84	9.763%	$185.3238	$185.32	$185.30	$185.30
Purchase #3	$18.41	4.238%	$19.1902	$19.19	$19.20	$19.20
Purchase #4	$222.74	3.198%	$229.8632	$229.86	$229.85	$229.90
Purchase #5	$134.51	3.481%	$139.1923	$139.19	$139.20	$139.20
Purchase #6	$102.54	13.693%	$116.5808	$116.58	$116.60	$116.60
Purchase #7	$104.84	7.430%	$112.6296	$112.63	$112.65	$112.60
7 purchase totals =	$940.45		$999.6093	$999.60	$999.65	$999.60