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	$53.49	10.811%	$59.2728	$59.27	$59.25	$59.30
Purchase #2	$101.40	10.207%	$111.7499	$111.75	$111.75	$111.70
Purchase #3	$25.45	10.374%	$28.0902	$28.09	$28.10	$28.10
Purchase #4	$18.70	8.387%	$20.2684	$20.27	$20.25	$20.30
Purchase #5	$70.28	6.542%	$74.8777	$74.88	$74.90	$74.90
Purchase #6	$67.27	7.660%	$72.4229	$72.42	$72.40	$72.40
Purchase #7	$115.82	3.388%	$119.744	$119.74	$119.75	$119.70
7 purchase totals =	$452.41		$486.4259	$486.42	$486.40	$486.40