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	$170.44	4.181%	$177.5661	$177.57	$177.55	$177.60
Purchase #2	$85.77	4.346%	$89.4976	$89.50	$89.50	$89.50
Purchase #3	$227.69	12.754%	$256.7296	$256.73	$256.75	$256.70
Purchase #4	$208.76	8.798%	$227.1267	$227.13	$227.15	$227.10
Purchase #5	$50.92	7.511%	$54.7446	$54.74	$54.75	$54.70
Purchase #6	$238.90	11.395%	$266.1227	$266.12	$266.10	$266.10
Purchase #7	$82.74	8.588%	$89.8457	$89.85	$89.85	$89.80
7 purchase totals =	$1,065.22		$1,161.6330	$1,161.64	$1,161.65	$1,161.50