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	$186.50	10.132%	$205.3962	$205.40	$205.40	$205.40
Purchase #2	$11.56	5.700%	$12.2189	$12.22	$12.20	$12.20
Purchase #3	$84.96	12.679%	$95.7321	$95.73	$95.75	$95.70
Purchase #4	$154.27	9.155%	$168.3934	$168.39	$168.40	$168.40
Purchase #5	$23.69	4.419%	$24.7369	$24.74	$24.75	$24.70
Purchase #6	$45.87	12.483%	$51.596	$51.60	$51.60	$51.60
Purchase #7	$103.68	4.469%	$108.3135	$108.31	$108.30	$108.30
7 purchase totals =	$610.53		$666.3870	$666.39	$666.40	$666.30