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	$93.38	9.852%	$102.5798	$102.58	$102.60	$102.60
Purchase #2	$76.50	9.280%	$83.5992	$83.60	$83.60	$83.60
Purchase #3	$41.88	13.453%	$47.5141	$47.51	$47.50	$47.50
Purchase #4	$33.87	10.595%	$37.4585	$37.46	$37.45	$37.50
Purchase #5	$54.63	12.257%	$61.326	$61.33	$61.35	$61.30
Purchase #6	$68.51	5.460%	$72.2506	$72.25	$72.25	$72.30
Purchase #7	$115.92	8.408%	$125.6666	$125.67	$125.65	$125.70
7 purchase totals =	$484.69		$530.3948	$530.40	$530.40	$530.50