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	$199.30	7.118%	$213.4862	$213.49	$213.50	$213.50
Purchase #2	$92.99	10.152%	$102.4303	$102.43	$102.45	$102.40
Purchase #3	$48.77	11.300%	$54.281	$54.28	$54.30	$54.30
Purchase #4	$102.31	10.269%	$112.8162	$112.82	$112.80	$112.80
Purchase #5	$7.88	8.295%	$8.5336	$8.53	$8.55	$8.50
Purchase #6	$57.56	8.646%	$62.5366	$62.54	$62.55	$62.50
Purchase #7	$239.74	7.103%	$256.7687	$256.77	$256.75	$256.80
7 purchase totals =	$748.55		$810.8526	$810.86	$810.90	$810.80