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	$209.87	6.216%	$222.9155	$222.92	$222.90	$222.90
Purchase #2	$114.73	10.430%	$126.6963	$126.70	$126.70	$126.70
Purchase #3	$143.43	11.286%	$159.6175	$159.62	$159.60	$159.60
Purchase #4	$103.42	8.304%	$112.008	$112.01	$112.00	$112.00
Purchase #5	$115.86	13.792%	$131.8394	$131.84	$131.85	$131.80
Purchase #6	$56.33	9.826%	$61.865	$61.87	$61.85	$61.90
Purchase #7	$195.40	8.347%	$211.71	$211.71	$211.70	$211.70
7 purchase totals =	$939.04		$1,026.6517	$1,026.67	$1,026.60	$1,026.60