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	$96.29	9.250%	$105.1968	$105.20	$105.20	$105.20
Purchase #2	$79.68	3.830%	$82.7317	$82.73	$82.75	$82.70
Purchase #3	$136.95	13.116%	$154.9124	$154.91	$154.90	$154.90
Purchase #4	$131.88	6.270%	$140.1489	$140.15	$140.15	$140.10
Purchase #5	$218.77	9.141%	$238.7678	$238.77	$238.75	$238.80
Purchase #6	$211.90	5.491%	$223.5354	$223.54	$223.55	$223.50
Purchase #7	$99.84	6.438%	$106.2677	$106.27	$106.25	$106.30
7 purchase totals =	$975.31		$1,051.5607	$1,051.57	$1,051.55	$1,051.50