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	$198.50	6.363%	$211.1306	$211.13	$211.15	$211.10
Purchase #2	$91.69	9.845%	$100.7169	$100.72	$100.70	$100.70
Purchase #3	$68.63	9.108%	$74.8808	$74.88	$74.90	$74.90
Purchase #4	$236.73	8.138%	$255.9951	$256.00	$256.00	$256.00
Purchase #5	$183.75	3.644%	$190.4459	$190.45	$190.45	$190.40
Purchase #6	$208.82	6.669%	$222.7462	$222.75	$222.75	$222.70
Purchase #7	$113.90	8.332%	$123.3901	$123.39	$123.40	$123.40
7 purchase totals =	$1,102.02		$1,179.3056	$1,179.32	$1,179.35	$1,179.20