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	$41.41	10.460%	$45.7415	$45.74	$45.75	$45.70
Purchase #2	$241.52	9.829%	$265.259	$265.26	$265.25	$265.30
Purchase #3	$12.28	6.199%	$13.0412	$13.04	$13.05	$13.00
Purchase #4	$220.70	8.208%	$238.8151	$238.82	$238.80	$238.80
Purchase #5	$94.92	5.383%	$100.0295	$100.03	$100.05	$100.00
Purchase #6	$245.40	9.142%	$267.8345	$267.83	$267.85	$267.80
Purchase #7	$76.72	12.347%	$86.1926	$86.19	$86.20	$86.20
7 purchase totals =	$932.95		$1,016.9134	$1,016.91	$1,016.95	$1,016.80