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	$179.98	9.309%	$196.7343	$196.73	$196.75	$196.70
Purchase #2	$225.48	13.609%	$256.1656	$256.17	$256.15	$256.20
Purchase #3	$124.83	12.751%	$140.7471	$140.75	$140.75	$140.70
Purchase #4	$35.97	11.319%	$40.0414	$40.04	$40.05	$40.00
Purchase #5	$87.53	8.660%	$95.1101	$95.11	$95.10	$95.10
Purchase #6	$161.96	13.386%	$183.64	$183.64	$183.65	$183.60
Purchase #7	$105.40	8.218%	$114.0618	$114.06	$114.05	$114.10
7 purchase totals =	$921.15		$1,026.5003	$1,026.50	$1,026.50	$1,026.40