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	$196.53	4.487%	$205.3483	$205.35	$205.35	$205.30
Purchase #2	$76.33	11.394%	$85.027	$85.03	$85.05	$85.00
Purchase #3	$165.69	12.241%	$185.9721	$185.97	$185.95	$186.00
Purchase #4	$75.69	9.566%	$82.9305	$82.93	$82.95	$82.90
Purchase #5	$77.82	10.210%	$85.7654	$85.77	$85.75	$85.80
Purchase #6	$159.59	8.341%	$172.9014	$172.90	$172.90	$172.90
Purchase #7	$54.76	5.449%	$57.7439	$57.74	$57.75	$57.70
7 purchase totals =	$806.41		$875.6886	$875.69	$875.70	$875.60