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	$144.62	3.464%	$149.6296	$149.63	$149.65	$149.60
Purchase #2	$212.63	12.809%	$239.8658	$239.87	$239.85	$239.90
Purchase #3	$98.81	7.632%	$106.3512	$106.35	$106.35	$106.40
Purchase #4	$89.51	11.504%	$99.8072	$99.81	$99.80	$99.80
Purchase #5	$127.78	12.517%	$143.7742	$143.77	$143.75	$143.80
Purchase #6	$52.70	3.781%	$54.6926	$54.69	$54.70	$54.70
Purchase #7	$243.83	5.315%	$256.7896	$256.79	$256.80	$256.80
7 purchase totals =	$969.88		$1,050.9102	$1,050.91	$1,050.90	$1,051.00