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	$227.82	3.416%	$235.6023	$235.60	$235.60	$235.60
Purchase #2	$159.35	6.450%	$169.6281	$169.63	$169.65	$169.60
Purchase #3	$77.29	3.841%	$80.2587	$80.26	$80.25	$80.30
Purchase #4	$28.72	9.742%	$31.5179	$31.52	$31.50	$31.50
Purchase #5	$128.40	8.856%	$139.7711	$139.77	$139.75	$139.80
Purchase #6	$249.35	13.299%	$282.5111	$282.51	$282.50	$282.50
Purchase #7	$112.41	10.157%	$123.8275	$123.83	$123.85	$123.80
7 purchase totals =	$983.34		$1,063.1167	$1,063.12	$1,063.10	$1,063.10