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	$135.50	5.814%	$143.378	$143.38	$143.40	$143.40
Purchase #2	$19.54	10.134%	$21.5202	$21.52	$21.50	$21.50
Purchase #3	$70.79	12.118%	$79.3683	$79.37	$79.35	$79.40
Purchase #4	$182.83	6.205%	$194.1746	$194.17	$194.15	$194.20
Purchase #5	$164.27	7.516%	$176.6165	$176.62	$176.60	$176.60
Purchase #6	$198.45	12.352%	$222.9625	$222.96	$222.95	$223.00
Purchase #7	$225.62	9.614%	$247.3111	$247.31	$247.30	$247.30
7 purchase totals =	$997.00		$1,085.3312	$1,085.33	$1,085.25	$1,085.40