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	$94.89	10.506%	$104.8591	$104.86	$104.85	$104.90
Purchase #2	$12.41	7.444%	$13.3338	$13.33	$13.35	$13.30
Purchase #3	$89.29	12.218%	$100.1995	$100.20	$100.20	$100.20
Purchase #4	$81.40	6.340%	$86.5608	$86.56	$86.55	$86.60
Purchase #5	$19.30	4.838%	$20.2337	$20.23	$20.25	$20.20
Purchase #6	$67.63	13.417%	$76.7039	$76.70	$76.70	$76.70
Purchase #7	$116.80	6.581%	$124.4866	$124.49	$124.50	$124.50
7 purchase totals =	$481.72		$526.3774	$526.37	$526.40	$526.40