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	$25.46	10.825%	$28.216	$28.22	$28.20	$28.20
Purchase #2	$58.90	3.741%	$61.1034	$61.10	$61.10	$61.10
Purchase #3	$37.39	3.724%	$38.7824	$38.78	$38.80	$38.80
Purchase #4	$6.71	4.242%	$6.9946	$6.99	$7.00	$7.00
Purchase #5	$78.44	10.406%	$86.6025	$86.60	$86.60	$86.60
Purchase #6	$238.47	8.381%	$258.4562	$258.46	$258.45	$258.50
Purchase #7	$245.61	12.220%	$275.6235	$275.62	$275.60	$275.60
7 purchase totals =	$690.98		$755.7786	$755.77	$755.75	$755.80