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	$123.89	5.755%	$131.0199	$131.02	$131.00	$131.00
Purchase #2	$195.89	10.127%	$215.7278	$215.73	$215.75	$215.70
Purchase #3	$189.97	7.259%	$203.7599	$203.76	$203.75	$203.80
Purchase #4	$111.80	10.677%	$123.7369	$123.74	$123.75	$123.70
Purchase #5	$208.66	6.185%	$221.5656	$221.57	$221.55	$221.60
Purchase #6	$118.30	7.645%	$127.344	$127.34	$127.35	$127.30
Purchase #7	$169.47	4.717%	$177.4639	$177.46	$177.45	$177.50
7 purchase totals =	$1,117.98		$1,200.6180	$1,200.62	$1,200.60	$1,200.60