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	$154.96	13.410%	$175.7401	$175.74	$175.75	$175.70
Purchase #2	$225.48	7.573%	$242.5556	$242.56	$242.55	$242.60
Purchase #3	$82.89	13.766%	$94.3006	$94.30	$94.30	$94.30
Purchase #4	$12.34	9.689%	$13.5356	$13.54	$13.55	$13.50
Purchase #5	$160.59	6.417%	$170.8951	$170.90	$170.90	$170.90
Purchase #6	$227.48	10.114%	$250.4873	$250.49	$250.50	$250.50
Purchase #7	$86.84	4.639%	$90.8685	$90.87	$90.85	$90.90
7 purchase totals =	$950.58		$1,038.3828	$1,038.40	$1,038.40	$1,038.40