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	$95.79	6.825%	$102.3277	$102.33	$102.35	$102.30
Purchase #2	$139.45	3.169%	$143.8692	$143.87	$143.85	$143.90
Purchase #3	$223.39	3.482%	$231.1684	$231.17	$231.15	$231.20
Purchase #4	$50.56	3.159%	$52.1572	$52.16	$52.15	$52.20
Purchase #5	$71.46	12.533%	$80.4161	$80.42	$80.40	$80.40
Purchase #6	$150.63	12.374%	$169.269	$169.27	$169.25	$169.30
Purchase #7	$111.69	4.174%	$116.3519	$116.35	$116.35	$116.40
7 purchase totals =	$842.97		$895.5595	$895.57	$895.50	$895.70