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	$21.62	4.793%	$22.6562	$22.66	$22.65	$22.70
Purchase #2	$160.93	13.351%	$182.4158	$182.42	$182.40	$182.40
Purchase #3	$36.72	10.807%	$40.6883	$40.69	$40.70	$40.70
Purchase #4	$227.83	4.643%	$238.4081	$238.41	$238.40	$238.40
Purchase #5	$203.98	8.813%	$221.9568	$221.96	$221.95	$222.00
Purchase #6	$212.36	10.320%	$234.2756	$234.28	$234.30	$234.30
Purchase #7	$76.31	4.145%	$79.473	$79.47	$79.45	$79.50
7 purchase totals =	$939.75		$1,019.8738	$1,019.89	$1,019.85	$1,020.00