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	$147.64	3.557%	$152.8916	$152.89	$152.90	$152.90
Purchase #2	$40.59	9.208%	$44.3275	$44.33	$44.35	$44.30
Purchase #3	$139.71	9.614%	$153.1417	$153.14	$153.15	$153.10
Purchase #4	$135.76	5.792%	$143.6232	$143.62	$143.60	$143.60
Purchase #5	$154.32	7.426%	$165.7798	$165.78	$165.80	$165.80
Purchase #6	$167.70	7.209%	$179.7895	$179.79	$179.80	$179.80
Purchase #7	$94.59	4.195%	$98.5581	$98.56	$98.55	$98.60
7 purchase totals =	$880.31		$938.1114	$938.11	$938.15	$938.10