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	$102.38	8.676%	$111.2625	$111.26	$111.25	$111.30
Purchase #2	$37.55	11.331%	$41.8048	$41.80	$41.80	$41.80
Purchase #3	$108.76	8.823%	$118.3559	$118.36	$118.35	$118.40
Purchase #4	$94.93	4.123%	$98.844	$98.84	$98.85	$98.80
Purchase #5	$198.71	11.450%	$221.4623	$221.46	$221.45	$221.50
Purchase #6	$135.34	3.350%	$139.8739	$139.87	$139.85	$139.90
Purchase #7	$248.93	13.386%	$282.2518	$282.25	$282.25	$282.30
7 purchase totals =	$926.60		$1,013.8552	$1,013.84	$1,013.80	$1,014.00