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	$92.77	4.327%	$96.7842	$96.78	$96.80	$96.80
Purchase #2	$94.90	10.651%	$105.0078	$105.01	$105.00	$105.00
Purchase #3	$216.68	7.253%	$232.3958	$232.40	$232.40	$232.40
Purchase #4	$19.40	6.593%	$20.679	$20.68	$20.70	$20.70
Purchase #5	$230.57	3.376%	$238.354	$238.35	$238.35	$238.40
Purchase #6	$232.61	7.362%	$249.7347	$249.73	$249.75	$249.70
Purchase #7	$173.25	13.389%	$196.4464	$196.45	$196.45	$196.40
7 purchase totals =	$1,060.18		$1,139.4019	$1,139.40	$1,139.45	$1,139.40