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	$50.98	3.485%	$52.7567	$52.76	$52.75	$52.80
Purchase #2	$72.90	13.577%	$82.7976	$82.80	$82.80	$82.80
Purchase #3	$22.90	11.742%	$25.5889	$25.59	$25.60	$25.60
Purchase #4	$130.38	13.284%	$147.6997	$147.70	$147.70	$147.70
Purchase #5	$207.78	8.425%	$225.2855	$225.29	$225.30	$225.30
Purchase #6	$44.62	8.231%	$48.2927	$48.29	$48.30	$48.30
Purchase #7	$184.82	6.197%	$196.2733	$196.27	$196.25	$196.30
7 purchase totals =	$714.38		$778.6944	$778.70	$778.70	$778.80