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	$161.67	8.597%	$175.5688	$175.57	$175.55	$175.60
Purchase #2	$82.54	8.144%	$89.2621	$89.26	$89.25	$89.30
Purchase #3	$78.76	9.129%	$85.95	$85.95	$85.95	$86.00
Purchase #4	$152.81	6.363%	$162.5333	$162.53	$162.55	$162.50
Purchase #5	$16.55	6.832%	$17.6807	$17.68	$17.70	$17.70
Purchase #6	$53.70	4.206%	$55.9586	$55.96	$55.95	$56.00
Purchase #7	$82.72	9.490%	$90.5701	$90.57	$90.55	$90.60
7 purchase totals =	$628.75		$677.5236	$677.52	$677.50	$677.70