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	$86.50	9.714%	$94.9026	$94.90	$94.90	$94.90
Purchase #2	$89.86	9.187%	$98.1154	$98.12	$98.10	$98.10
Purchase #3	$20.47	6.195%	$21.7381	$21.74	$21.75	$21.70
Purchase #4	$61.69	7.747%	$66.4691	$66.47	$66.45	$66.50
Purchase #5	$131.88	12.621%	$148.5246	$148.52	$148.50	$148.50
Purchase #6	$16.50	12.417%	$18.5488	$18.55	$18.55	$18.50
Purchase #7	$89.47	3.163%	$92.2999	$92.30	$92.30	$92.30
7 purchase totals =	$496.37		$540.5985	$540.60	$540.55	$540.50