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	$55.59	6.800%	$59.3701	$59.37	$59.35	$59.40
Purchase #2	$30.44	5.740%	$32.1873	$32.19	$32.20	$32.20
Purchase #3	$178.38	7.588%	$191.9155	$191.92	$191.90	$191.90
Purchase #4	$243.91	5.603%	$257.5763	$257.58	$257.60	$257.60
Purchase #5	$225.85	6.554%	$240.6522	$240.65	$240.65	$240.70
Purchase #6	$120.54	10.737%	$133.4824	$133.48	$133.50	$133.50
Purchase #7	$123.40	6.120%	$130.9521	$130.95	$130.95	$131.00
7 purchase totals =	$978.11		$1,046.1359	$1,046.14	$1,046.15	$1,046.30