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	$20.31	12.432%	$22.8349	$22.83	$22.85	$22.80
Purchase #2	$80.64	11.478%	$89.8959	$89.90	$89.90	$89.90
Purchase #3	$56.52	12.768%	$63.7365	$63.74	$63.75	$63.70
Purchase #4	$99.54	5.233%	$104.7489	$104.75	$104.75	$104.70
Purchase #5	$162.25	8.393%	$175.8676	$175.87	$175.85	$175.90
Purchase #6	$103.63	6.777%	$110.653	$110.65	$110.65	$110.70
Purchase #7	$111.80	6.316%	$118.8613	$118.86	$118.85	$118.90
7 purchase totals =	$634.69		$686.5981	$686.60	$686.60	$686.60