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	$70.50	9.399%	$77.1263	$77.13	$77.15	$77.10
Purchase #2	$200.93	12.858%	$226.7656	$226.77	$226.75	$226.80
Purchase #3	$117.46	11.662%	$131.1582	$131.16	$131.15	$131.20
Purchase #4	$109.72	12.533%	$123.4712	$123.47	$123.45	$123.50
Purchase #5	$189.59	4.719%	$198.5368	$198.54	$198.55	$198.50
Purchase #6	$207.98	13.384%	$235.816	$235.82	$235.80	$235.80
Purchase #7	$93.94	13.398%	$106.5261	$106.53	$106.55	$106.50
7 purchase totals =	$990.12		$1,099.4002	$1,099.42	$1,099.40	$1,099.40