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	$110.48	4.667%	$115.6361	$115.64	$115.65	$115.60
Purchase #2	$64.51	4.263%	$67.2601	$67.26	$67.25	$67.30
Purchase #3	$242.88	5.106%	$255.2815	$255.28	$255.30	$255.30
Purchase #4	$52.56	13.430%	$59.6188	$59.62	$59.60	$59.60
Purchase #5	$18.25	7.501%	$19.6189	$19.62	$19.60	$19.60
Purchase #6	$192.32	13.829%	$218.9159	$218.92	$218.90	$218.90
Purchase #7	$55.90	5.273%	$58.8476	$58.85	$58.85	$58.80
7 purchase totals =	$736.90		$795.1789	$795.19	$795.15	$795.10