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	$167.50	13.516%	$190.1393	$190.14	$190.15	$190.10
Purchase #2	$214.48	4.489%	$224.108	$224.11	$224.10	$224.10
Purchase #3	$86.25	4.829%	$90.415	$90.42	$90.40	$90.40
Purchase #4	$103.62	10.853%	$114.8659	$114.87	$114.85	$114.90
Purchase #5	$90.33	9.275%	$98.7081	$98.71	$98.70	$98.70
Purchase #6	$6.63	11.568%	$7.397	$7.40	$7.40	$7.40
Purchase #7	$80.61	11.680%	$90.0252	$90.03	$90.05	$90.00
7 purchase totals =	$749.42		$815.6585	$815.68	$815.65	$815.60