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	$45.87	4.311%	$47.8475	$47.85	$47.85	$47.80
Purchase #2	$8.30	11.797%	$9.2792	$9.28	$9.30	$9.30
Purchase #3	$163.35	7.121%	$174.9822	$174.98	$175.00	$175.00
Purchase #4	$58.76	13.842%	$66.8936	$66.89	$66.90	$66.90
Purchase #5	$179.36	9.280%	$196.0046	$196.00	$196.00	$196.00
Purchase #6	$21.92	11.369%	$24.4121	$24.41	$24.40	$24.40
Purchase #7	$137.82	7.512%	$148.173	$148.17	$148.15	$148.20
7 purchase totals =	$615.38		$667.5922	$667.58	$667.60	$667.60