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	$89.38	12.287%	$100.3621	$100.36	$100.35	$100.40
Purchase #2	$60.68	3.503%	$62.8056	$62.81	$62.80	$62.80
Purchase #3	$40.84	6.436%	$43.4685	$43.47	$43.45	$43.50
Purchase #4	$130.64	8.515%	$141.764	$141.76	$141.75	$141.80
Purchase #5	$138.88	3.370%	$143.5603	$143.56	$143.55	$143.60
Purchase #6	$91.63	3.174%	$94.5383	$94.54	$94.55	$94.50
Purchase #7	$185.34	10.521%	$204.8396	$204.84	$204.85	$204.80
7 purchase totals =	$737.39		$791.3384	$791.34	$791.30	$791.40