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	$169.67	12.285%	$190.514	$190.51	$190.50	$190.50
Purchase #2	$49.81	4.323%	$51.9633	$51.96	$51.95	$52.00
Purchase #3	$171.98	9.368%	$188.0911	$188.09	$188.10	$188.10
Purchase #4	$45.32	12.216%	$50.8563	$50.86	$50.85	$50.90
Purchase #5	$61.55	7.825%	$66.3663	$66.37	$66.35	$66.40
Purchase #6	$108.86	8.608%	$118.2307	$118.23	$118.25	$118.20
Purchase #7	$106.32	11.109%	$118.1311	$118.13	$118.15	$118.10
7 purchase totals =	$713.51		$784.1528	$784.15	$784.15	$784.20