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	$82.68	4.334%	$86.2634	$86.26	$86.25	$86.30
Purchase #2	$116.38	6.449%	$123.8853	$123.89	$123.90	$123.90
Purchase #3	$192.74	13.758%	$219.2572	$219.26	$219.25	$219.30
Purchase #4	$151.48	7.289%	$162.5214	$162.52	$162.50	$162.50
Purchase #5	$147.34	12.110%	$165.1829	$165.18	$165.20	$165.20
Purchase #6	$130.68	13.689%	$148.5688	$148.57	$148.55	$148.60
Purchase #7	$130.44	4.521%	$136.3372	$136.34	$136.35	$136.30
7 purchase totals =	$951.74		$1,042.0162	$1,042.02	$1,042.00	$1,042.10