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	$99.25	7.461%	$106.655	$106.66	$106.65	$106.70
Purchase #2	$86.48	6.211%	$91.8513	$91.85	$91.85	$91.90
Purchase #3	$91.69	9.157%	$100.0861	$100.09	$100.10	$100.10
Purchase #4	$123.34	13.618%	$140.1364	$140.14	$140.15	$140.10
Purchase #5	$46.88	13.626%	$53.2679	$53.27	$53.25	$53.30
Purchase #6	$29.84	13.831%	$33.9672	$33.97	$33.95	$34.00
Purchase #7	$187.80	6.520%	$200.0446	$200.04	$200.05	$200.00
7 purchase totals =	$665.28		$726.0085	$726.02	$726.00	$726.10