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	$55.40	10.181%	$61.0403	$61.04	$61.05	$61.00
Purchase #2	$72.40	8.303%	$78.4114	$78.41	$78.40	$78.40
Purchase #3	$176.63	5.319%	$186.0249	$186.02	$186.00	$186.00
Purchase #4	$81.37	9.801%	$89.3451	$89.35	$89.35	$89.30
Purchase #5	$204.30	8.386%	$221.4326	$221.43	$221.45	$221.40
Purchase #6	$243.29	7.835%	$262.3518	$262.35	$262.35	$262.40
Purchase #7	$211.95	12.397%	$238.2254	$238.23	$238.25	$238.20
7 purchase totals =	$1,045.34		$1,136.8315	$1,136.83	$1,136.85	$1,136.70