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	$182.46	8.797%	$198.511	$198.51	$198.50	$198.50
Purchase #2	$138.49	10.266%	$152.7074	$152.71	$152.70	$152.70
Purchase #3	$52.73	13.289%	$59.7373	$59.74	$59.75	$59.70
Purchase #4	$173.74	10.293%	$191.6231	$191.62	$191.60	$191.60
Purchase #5	$73.59	7.141%	$78.8451	$78.85	$78.85	$78.80
Purchase #6	$237.57	8.610%	$258.0248	$258.02	$258.00	$258.00
Purchase #7	$151.81	10.195%	$167.287	$167.29	$167.30	$167.30
7 purchase totals =	$1,010.39		$1,106.7357	$1,106.74	$1,106.70	$1,106.60