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	$204.85	6.651%	$218.4746	$218.47	$218.45	$218.50
Purchase #2	$242.45	5.731%	$256.3448	$256.34	$256.35	$256.30
Purchase #3	$161.50	3.522%	$167.188	$167.19	$167.20	$167.20
Purchase #4	$193.60	7.576%	$208.2671	$208.27	$208.25	$208.30
Purchase #5	$243.33	10.147%	$268.0207	$268.02	$268.00	$268.00
Purchase #6	$175.37	12.156%	$196.688	$196.69	$196.70	$196.70
Purchase #7	$192.30	7.580%	$206.8763	$206.88	$206.90	$206.90
7 purchase totals =	$1,413.40		$1,521.8595	$1,521.86	$1,521.85	$1,521.90