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	$42.83	6.385%	$45.5647	$45.56	$45.55	$45.60
Purchase #2	$82.66	8.736%	$89.8812	$89.88	$89.90	$89.90
Purchase #3	$29.43	5.336%	$31.0004	$31.00	$31.00	$31.00
Purchase #4	$186.38	13.630%	$211.7836	$211.78	$211.80	$211.80
Purchase #5	$56.86	10.438%	$62.795	$62.80	$62.80	$62.80
Purchase #6	$113.98	4.209%	$118.7774	$118.78	$118.80	$118.80
Purchase #7	$166.85	4.416%	$174.2181	$174.22	$174.20	$174.20
7 purchase totals =	$678.99		$734.0204	$734.02	$734.05	$734.10