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	$21.32	11.164%	$23.7002	$23.70	$23.70	$23.70
Purchase #2	$90.28	11.315%	$100.4952	$100.50	$100.50	$100.50
Purchase #3	$31.66	13.140%	$35.8201	$35.82	$35.80	$35.80
Purchase #4	$103.43	6.210%	$109.853	$109.85	$109.85	$109.90
Purchase #5	$99.68	5.551%	$105.2132	$105.21	$105.20	$105.20
Purchase #6	$141.55	4.112%	$147.3705	$147.37	$147.35	$147.40
Purchase #7	$161.49	10.838%	$178.9923	$178.99	$179.00	$179.00
7 purchase totals =	$649.41		$701.4445	$701.44	$701.40	$701.50