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	$171.77	3.855%	$178.3917	$178.39	$178.40	$178.40
Purchase #2	$184.56	4.503%	$192.8707	$192.87	$192.85	$192.90
Purchase #3	$36.56	4.440%	$38.1833	$38.18	$38.20	$38.20
Purchase #4	$115.97	6.387%	$123.377	$123.38	$123.40	$123.40
Purchase #5	$123.46	10.258%	$136.1245	$136.12	$136.10	$136.10
Purchase #6	$193.72	12.677%	$218.2779	$218.28	$218.30	$218.30
Purchase #7	$116.30	6.258%	$123.5781	$123.58	$123.60	$123.60
7 purchase totals =	$942.34		$1,010.8032	$1,010.80	$1,010.85	$1,010.90