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	$62.59	12.443%	$70.3781	$70.38	$70.40	$70.40
Purchase #2	$22.40	13.746%	$25.4791	$25.48	$25.50	$25.50
Purchase #3	$97.76	6.335%	$103.9531	$103.95	$103.95	$104.00
Purchase #4	$123.84	8.595%	$134.484	$134.48	$134.50	$134.50
Purchase #5	$250.92	11.444%	$279.6353	$279.64	$279.65	$279.60
Purchase #6	$55.33	8.185%	$59.8588	$59.86	$59.85	$59.90
Purchase #7	$77.50	7.442%	$83.2676	$83.27	$83.25	$83.30
7 purchase totals =	$690.34		$757.0560	$757.06	$757.10	$757.20